Enabling CPP doxygen API docs build (#6346)
Enabling CPP doxygen API docs build (#6346)

* Enabling CPP doxygen API docs build

* Enabling CPP API docs

jamesliu/mxnet,LinkHS/incubator-mxnet,fullfanta/mxnet,yajiedesign/mxnet,dmlc/mxnet,lxn2/mxnet,yuruofeifei/mxnet,zhreshold/mxnet,Ldpe2G/mxnet,rahul003/mxnet,antoan2/incubator-mxnet,antoan2/incubator-mxnet,reminisce/mxnet,tornadomeet/mxnet,precedenceguo/mxnet,indhub/mxnet,thirdwing/mxnet,coder-james/mxnet,EvanzzzZ/mxnet,Northrend/mxnet,dmlc/mxnet,kevinthesun/mxnet,yajiedesign/mxnet,jiajiechen/mxnet,Prasad9/incubator-mxnet,arank/mxnet,arank/mxnet,reminisce/mxnet,stefanhenneking/mxnet,kevinthesun/mxnet,ForkedReposBak/mxnet,yajiedesign/mxnet,stefanhenneking/mxnet,EvanzzzZ/mxnet,EvanzzzZ/mxnet,EvanzzzZ/mxnet,sergeykolychev/mxnet,pluskid/mxnet,szha/mxnet,pluskid/mxnet,TuSimple/mxnet,ZihengJiang/mxnet,weleen/mxnet,dmlc/mxnet,jermainewang/mxnet,apaleyes/mxnet,DickJC123/mxnet,arikpoz/mxnet,hesseltuinhof/mxnet,TuSimple/mxnet,rahul003/mxnet,larroy/mxnet,gautamkmr/incubator-mxnet,kevinthesun/mxnet,DickJC123/mxnet,apaleyes/mxnet,thirdwing/mxnet,CodingCat/mxnet,eric-haibin-lin/mxnet,apaleyes/mxnet,TuSimple/mxnet,precedenceguo/mxnet,thirdwing/mxnet,navrasio/mxnet,szha/mxnet,leezu/mxnet,navrasio/mxnet,danithaca/mxnet,apache/incubator-mxnet,navrasio/mxnet,hotpxl/mxnet,tlby/mxnet,dmlc/mxnet,smolix/incubator-mxnet,vikingMei/mxnet,madjam/mxnet,crazy-cat/incubator-mxnet,hotpxl/mxnet,ykim362/mxnet,Prasad9/incubator-mxnet,crazy-cat/incubator-mxnet,precedenceguo/mxnet,arikpoz/mxnet,Prasad9/incubator-mxnet,solin319/incubator-mxnet,solin319/incubator-mxnet,LinkHS/incubator-mxnet,ptrendx/mxnet,tlby/mxnet,jamesliu/mxnet,navrasio/mxnet,navrasio/mxnet,TuSimple/mxnet,danithaca/mxnet,eric-haibin-lin/mxnet,leezu/mxnet,lxn2/mxnet,kkk669/mxnet,hesseltuinhof/mxnet,DR08/mxnet,vikingMei/mxnet,danithaca/mxnet,yuruofeifei/mxnet,jamesliu/mxnet,TuSimple/mxnet,mbaijal/incubator-mxnet,CodingCat/mxnet,yuruofeifei/mxnet,Northrend/mxnet,Ldpe2G/mxnet,madjam/mxnet,Mega-DatA-Lab/mxnet,Mega-DatA-Lab/mxnet,larroy/mxnet,lxn2/mxnet,jennyzhang0215/incubator-mxnet,sergeykolychev/mxnet,jamesliu/mxnet,weleen/mxnet,mbaijal/incubator-mxnet,hpi-xnor/BMXNet,zhreshold/mxnet,ZihengJiang/mxnet,ykim362/mxnet,sergeykolychev/mxnet,yajiedesign/mxnet,wangyum/mxnet,yuruofeifei/mxnet,ForkedReposBak/mxnet,DR08/mxnet,kevinthesun/mxnet,Prasad9/incubator-mxnet,hpi-xnor/BMXNet,formath/mxnet,nicklhy/mxnet,crazy-cat/incubator-mxnet,mbaijal/incubator-mxnet,zhreshold/mxnet,hpi-xnor/BMXNet,tlby/mxnet,solin319/incubator-mxnet,stefanhenneking/mxnet,tlby/mxnet,ptrendx/mxnet,kevinthesun/mxnet,tornadomeet/mxnet,jiajiechen/mxnet,Northrend/mxnet,danithaca/mxnet,precedenceguo/mxnet,eric-haibin-lin/mxnet,Northrend/mxnet,solin319/incubator-mxnet,navrasio/mxnet,pluskid/mxnet,solin319/incubator-mxnet,ZihengJiang/mxnet,DR08/mxnet,arikpoz/mxnet,xcgoner/dist-mxnet,danithaca/mxnet,yajiedesign/mxnet,indhub/mxnet,CodingCat/mxnet,leezu/mxnet,sxjscience/mxnet,ykim362/mxnet,leezu/mxnet,piiswrong/mxnet,luoyetx/mxnet,rahul003/mxnet,zhreshold/mxnet,ForkedReposBak/mxnet,leezu/mxnet,tlby/mxnet,dmlc/mxnet,jennyzhang0215/incubator-mxnet,coder-james/mxnet,jermainewang/mxnet,precedenceguo/mxnet,jennyzhang0215/incubator-mxnet,yuruofeifei/mxnet,hesseltuinhof/mxnet,zhreshold/mxnet,tornadomeet/mxnet,sergeykolychev/mxnet,jennyzhang0215/incubator-mxnet,hesseltuinhof/mxnet,coder-james/mxnet,stefanhenneking/mxnet,tlby/mxnet,arank/mxnet,coder-james/mxnet,saurabh3949/mxnet,xcgoner/dist-mxnet,antoan2/incubator-mxnet,ykim362/mxnet,Mega-DatA-Lab/mxnet,antoan2/incubator-mxnet,gautamkmr/incubator-mxnet,kevinthesun/mxnet,dmlc/mxnet,kkk669/mxnet,ykim362/mxnet,hotpxl/mxnet,fullfanta/mxnet,piiswrong/mxnet,rahul003/mxnet,reminisce/mxnet,pluskid/mxnet,luoyetx/mxnet,LinkHS/incubator-mxnet,apache/incubator-mxnet,saurabh3949/mxnet,thirdwing/mxnet,ptrendx/mxnet,jamesliu/mxnet,dmlc/mxnet,yajiedesign/mxnet,ptrendx/mxnet,mbaijal/incubator-mxnet,saurabh3949/mxnet,precedenceguo/mxnet,apaleyes/mxnet,saurabh3949/mxnet,apaleyes/mxnet,smolix/incubator-mxnet,szha/mxnet,tornadomeet/mxnet,rahul003/mxnet,nicklhy/mxnet,tornadomeet/mxnet,DR08/mxnet,hotpxl/mxnet,LinkHS/incubator-mxnet,szha/mxnet,larroy/mxnet,Mega-DatA-Lab/mxnet,lxn2/mxnet,xcgoner/dist-mxnet,danithaca/mxnet,solin319/incubator-mxnet,smolix/incubator-mxnet,smolix/incubator-mxnet,reminisce/mxnet,solin319/incubator-mxnet,coder-james/mxnet,Northrend/mxnet,Prasad9/incubator-mxnet,piiswrong/mxnet,sxjscience/mxnet,Prasad9/incubator-mxnet,kkk669/mxnet,yuruofeifei/mxnet,kkk669/mxnet,sxjscience/mxnet,wangyum/mxnet,vikingMei/mxnet,sxjscience/mxnet,indhub/mxnet,eric-haibin-lin/mxnet,hpi-xnor/BMXNet,Ldpe2G/mxnet,jamesliu/mxnet,EvanzzzZ/mxnet,precedenceguo/mxnet,dmlc/mxnet,ForkedReposBak/mxnet,rahul003/mxnet,CodingCat/mxnet,formath/mxnet,apaleyes/mxnet,smolix/incubator-mxnet,lxn2/mxnet,stefanhenneking/mxnet,reminisce/mxnet,antoan2/incubator-mxnet,sxjscience/mxnet,vikingMei/mxnet,LinkHS/incubator-mxnet,danithaca/mxnet,hpi-xnor/BMXNet,LinkHS/incubator-mxnet,eric-haibin-lin/mxnet,apaleyes/mxnet,vikingMei/mxnet,Ldpe2G/mxnet,nicklhy/mxnet,sxjscience/mxnet,wangyum/mxnet,xcgoner/dist-mxnet,formath/mxnet,Mega-DatA-Lab/mxnet,larroy/mxnet,jennyzhang0215/incubator-mxnet,solin319/incubator-mxnet,weleen/mxnet,mbaijal/incubator-mxnet,lxn2/mxnet,jermainewang/mxnet,DickJC123/mxnet,saurabh3949/mxnet,antoan2/incubator-mxnet,zhreshold/mxnet,crazy-cat/incubator-mxnet,larroy/mxnet,hesseltuinhof/mxnet,LinkHS/incubator-mxnet,leezu/mxnet,lxn2/mxnet,tlby/mxnet,Ldpe2G/mxnet,Mega-DatA-Lab/mxnet,jennyzhang0215/incubator-mxnet,tlby/mxnet,sergeykolychev/mxnet,ShownX/incubator-mxnet,jermainewang/mxnet,jiajiechen/mxnet,DR08/mxnet,jennyzhang0215/incubator-mxnet,zhreshold/mxnet,szha/mxnet,thirdwing/mxnet,weleen/mxnet,TuSimple/mxnet,ShownX/incubator-mxnet,EvanzzzZ/mxnet,xcgoner/dist-mxnet,apache/incubator-mxnet,szha/mxnet,Ldpe2G/mxnet,gautamkmr/incubator-mxnet,arikpoz/mxnet,stefanhenneking/mxnet,wangyum/mxnet,piiswrong/mxnet,madjam/mxnet,kevinthesun/mxnet,Ldpe2G/mxnet,Northrend/mxnet,indhub/mxnet,crazy-cat/incubator-mxnet,hpi-xnor/BMXNet,arikpoz/mxnet,CodingCat/mxnet,arank/mxnet,ForkedReposBak/mxnet,ForkedReposBak/mxnet,Northrend/mxnet,formath/mxnet,reminisce/mxnet,EvanzzzZ/mxnet,fullfanta/mxnet,saurabh3949/mxnet,madjam/mxnet,stefanhenneking/mxnet,pluskid/mxnet,jermainewang/mxnet,apache/incubator-mxnet,jiajiechen/mxnet,formath/mxnet,danithaca/mxnet,Mega-DatA-Lab/mxnet,piiswrong/mxnet,indhub/mxnet,saurabh3949/mxnet,eric-haibin-lin/mxnet,DR08/mxnet,tornadomeet/mxnet,tornadomeet/mxnet,ykim362/mxnet,antoan2/incubator-mxnet,eric-haibin-lin/mxnet,navrasio/mxnet,yuruofeifei/mxnet,ShownX/incubator-mxnet,smolix/incubator-mxnet,TuSimple/mxnet,indhub/mxnet,madjam/mxnet,navrasio/mxnet,piiswrong/mxnet,DR08/mxnet,jiajiechen/mxnet,ForkedReposBak/mxnet,luoyetx/mxnet,TuSimple/mxnet,ptrendx/mxnet,eric-haibin-lin/mxnet,luoyetx/mxnet,wangyum/mxnet,thirdwing/mxnet,jermainewang/mxnet,crazy-cat/incubator-mxnet,arank/mxnet,hotpxl/mxnet,weleen/mxnet,weleen/mxnet,jiajiechen/mxnet,danithaca/mxnet,pluskid/mxnet,ForkedReposBak/mxnet,ptrendx/mxnet,piiswrong/mxnet,jamesliu/mxnet,thirdwing/mxnet,CodingCat/mxnet,arikpoz/mxnet,smolix/incubator-mxnet,formath/mxnet,Mega-DatA-Lab/mxnet,kkk669/mxnet,ptrendx/mxnet,piiswrong/mxnet,reminisce/mxnet,arank/mxnet,rahul003/mxnet,arikpoz/mxnet,hpi-xnor/BMXNet,kkk669/mxnet,tlby/mxnet,leezu/mxnet,antoan2/incubator-mxnet,hesseltuinhof/mxnet,ZihengJiang/mxnet,szha/mxnet,piiswrong/mxnet,reminisce/mxnet,luoyetx/mxnet,mbaijal/incubator-mxnet,gautamkmr/incubator-mxnet,ZihengJiang/mxnet,jamesliu/mxnet,jermainewang/mxnet,wangyum/mxnet,jennyzhang0215/incubator-mxnet,mbaijal/incubator-mxnet,jiajiechen/mxnet,nicklhy/mxnet,saurabh3949/mxnet,kevinthesun/mxnet,DR08/mxnet,weleen/mxnet,ptrendx/mxnet,kkk669/mxnet,zhreshold/mxnet,madjam/mxnet,antoan2/incubator-mxnet,coder-james/mxnet,reminisce/mxnet,jennyzhang0215/incubator-mxnet,Prasad9/incubator-mxnet,sxjscience/mxnet,hesseltuinhof/mxnet,fullfanta/mxnet,sxjscience/mxnet,szha/mxnet,LinkHS/incubator-mxnet,indhub/mxnet,hotpxl/mxnet,weleen/mxnet,ptrendx/mxnet,jiajiechen/mxnet,nicklhy/mxnet,rahul003/mxnet,saurabh3949/mxnet,ShownX/incubator-mxnet,ptrendx/mxnet,yajiedesign/mxnet,wangyum/mxnet,hpi-xnor/BMXNet,madjam/mxnet,hpi-xnor/BMXNet,tornadomeet/mxnet,ShownX/incubator-mxnet,crazy-cat/incubator-mxnet,ykim362/mxnet,CodingCat/mxnet,rahul003/mxnet,Ldpe2G/mxnet,xcgoner/dist-mxnet,arank/mxnet,coder-james/mxnet,lxn2/mxnet,Northrend/mxnet,DickJC123/mxnet,indhub/mxnet,tornadomeet/mxnet,nicklhy/mxnet,Prasad9/incubator-mxnet,gautamkmr/incubator-mxnet,lxn2/mxnet,ShownX/incubator-mxnet,mbaijal/incubator-mxnet,thirdwing/mxnet,sergeykolychev/mxnet,reminisce/mxnet,kevinthesun/mxnet,fullfanta/mxnet,hotpxl/mxnet,stefanhenneking/mxnet,jamesliu/mxnet,ykim362/mxnet,thirdwing/mxnet,Ldpe2G/mxnet,ShownX/incubator-mxnet,larroy/mxnet,nicklhy/mxnet,zhreshold/mxnet,luoyetx/mxnet,nicklhy/mxnet,mbaijal/incubator-mxnet,hesseltuinhof/mxnet,crazy-cat/incubator-mxnet,weleen/mxnet,ShownX/incubator-mxnet,hesseltuinhof/mxnet,arikpoz/mxnet,EvanzzzZ/mxnet,indhub/mxnet,wangyum/mxnet,sxjscience/mxnet,fullfanta/mxnet,larroy/mxnet,solin319/incubator-mxnet,hotpxl/mxnet,xcgoner/dist-mxnet,yajiedesign/mxnet,szha/mxnet,hotpxl/mxnet,formath/mxnet,precedenceguo/mxnet,arikpoz/mxnet,sergeykolychev/mxnet,pluskid/mxnet,ShownX/incubator-mxnet,gautamkmr/incubator-mxnet,LinkHS/incubator-mxnet,Prasad9/incubator-mxnet,madjam/mxnet,fullfanta/mxnet,pluskid/mxnet,jiajiechen/mxnet,stefanhenneking/mxnet,Northrend/mxnet,CodingCat/mxnet,gautamkmr/incubator-mxnet,nicklhy/mxnet,jermainewang/mxnet,yuruofeifei/mxnet,kkk669/mxnet,fullfanta/mxnet,vikingMei/mxnet,luoyetx/mxnet,vikingMei/mxnet,arank/mxnet,CodingCat/mxnet,xcgoner/dist-mxnet,gautamkmr/incubator-mxnet,ZihengJiang/mxnet,apaleyes/mxnet,ZihengJiang/mxnet,yajiedesign/mxnet,coder-james/mxnet,ZihengJiang/mxnet,kkk669/mxnet,yuruofeifei/mxnet,tlby/mxnet,madjam/mxnet,fullfanta/mxnet,precedenceguo/mxnet,EvanzzzZ/mxnet,arank/mxnet,dmlc/mxnet,xcgoner/dist-mxnet,smolix/incubator-mxnet,coder-james/mxnet,gautamkmr/incubator-mxnet,TuSimple/mxnet,crazy-cat/incubator-mxnet,sergeykolychev/mxnet,leezu/mxnet,pluskid/mxnet,luoyetx/mxnet,formath/mxnet,larroy/mxnet,wangyum/mxnet,ForkedReposBak/mxnet,larroy/mxnet,formath/mxnet,vikingMei/mxnet,vikingMei/mxnet,ykim362/mxnet,TuSimple/mxnet,smolix/incubator-mxnet,jermainewang/mxnet,sergeykolychev/mxnet,leezu/mxnet,apaleyes/mxnet,Mega-DatA-Lab/mxnet,DR08/mxnet,eric-haibin-lin/mxnet,navrasio/mxnet,ZihengJiang/mxnet,luoyetx/mxnet