add MSRAPrelu initializer for cpp-package (#9121)
add MSRAPrelu initializer for cpp-package (#9121)

* add MSRAPrelu initializer for cpp-package

hello, this change adds the MSRAPrelu initializer for cpp-package, which follows the python code
```
//     def __init__(self, factor_type="avg", slope=0.25):
//         magnitude = 2. / (1 + slope ** 2)
//         super(MSRAPrelu, self).__init__("gaussian", factor_type, magnitude)
//         self._kwargs = {'factor_type': factor_type, 'slope': slope}
```

* change indent

* declare explicit

mbaijal/incubator-mxnet,CodingCat/mxnet,TuSimple/mxnet,yajiedesign/mxnet,CodingCat/mxnet,larroy/mxnet,sxjscience/mxnet,zhreshold/mxnet,weleen/mxnet,apache/incubator-mxnet,precedenceguo/mxnet,reminisce/mxnet,navrasio/mxnet,tlby/mxnet,szha/mxnet,tlby/mxnet,CodingCat/mxnet,jiajiechen/mxnet,zhreshold/mxnet,Northrend/mxnet,CodingCat/mxnet,navrasio/mxnet,vikingMei/mxnet,dmlc/mxnet,szha/mxnet,rahul003/mxnet,mbaijal/incubator-mxnet,yajiedesign/mxnet,jamesliu/mxnet,sxjscience/mxnet,apache/incubator-mxnet,navrasio/mxnet,sxjscience/mxnet,fullfanta/mxnet,jiajiechen/mxnet,indhub/mxnet,fullfanta/mxnet,jiajiechen/mxnet,yajiedesign/mxnet,navrasio/mxnet,fullfanta/mxnet,szha/mxnet,szha/mxnet,Northrend/mxnet,TuSimple/mxnet,luoyetx/mxnet,TuSimple/mxnet,zhreshold/mxnet,ptrendx/mxnet,eric-haibin-lin/mxnet,CodingCat/mxnet,fullfanta/mxnet,rahul003/mxnet,fullfanta/mxnet,weleen/mxnet,vikingMei/mxnet,fullfanta/mxnet,CodingCat/mxnet,ptrendx/mxnet,mbaijal/incubator-mxnet,eric-haibin-lin/mxnet,tornadomeet/mxnet,eric-haibin-lin/mxnet,reminisce/mxnet,yajiedesign/mxnet,jiajiechen/mxnet,leezu/mxnet,eric-haibin-lin/mxnet,ForkedReposBak/mxnet,rahul003/mxnet,vikingMei/mxnet,tlby/mxnet,sxjscience/mxnet,precedenceguo/mxnet,Northrend/mxnet,precedenceguo/mxnet,sxjscience/mxnet,vikingMei/mxnet,vikingMei/mxnet,dmlc/mxnet,rahul003/mxnet,dmlc/mxnet,LinkHS/incubator-mxnet,weleen/mxnet,zhreshold/mxnet,dmlc/mxnet,luoyetx/mxnet,larroy/mxnet,reminisce/mxnet,Northrend/mxnet,ForkedReposBak/mxnet,ptrendx/mxnet,fullfanta/mxnet,jiajiechen/mxnet,ptrendx/mxnet,TuSimple/mxnet,LinkHS/incubator-mxnet,tornadomeet/mxnet,sxjscience/mxnet,Northrend/mxnet,luoyetx/mxnet,fullfanta/mxnet,tlby/mxnet,luoyetx/mxnet,eric-haibin-lin/mxnet,indhub/mxnet,weleen/mxnet,DickJC123/mxnet,DickJC123/mxnet,tlby/mxnet,precedenceguo/mxnet,leezu/mxnet,leezu/mxnet,tornadomeet/mxnet,mbaijal/incubator-mxnet,reminisce/mxnet,yajiedesign/mxnet,tlby/mxnet,navrasio/mxnet,weleen/mxnet,fullfanta/mxnet,precedenceguo/mxnet,larroy/mxnet,larroy/mxnet,jamesliu/mxnet,CodingCat/mxnet,sxjscience/mxnet,jamesliu/mxnet,yajiedesign/mxnet,yajiedesign/mxnet,reminisce/mxnet,ptrendx/mxnet,ForkedReposBak/mxnet,leezu/mxnet,LinkHS/incubator-mxnet,larroy/mxnet,precedenceguo/mxnet,tornadomeet/mxnet,jamesliu/mxnet,weleen/mxnet,ForkedReposBak/mxnet,mbaijal/incubator-mxnet,szha/mxnet,eric-haibin-lin/mxnet,szha/mxnet,mbaijal/incubator-mxnet,ForkedReposBak/mxnet,indhub/mxnet,ForkedReposBak/mxnet,ptrendx/mxnet,rahul003/mxnet,reminisce/mxnet,zhreshold/mxnet,apache/incubator-mxnet,weleen/mxnet,jiajiechen/mxnet,tornadomeet/mxnet,leezu/mxnet,reminisce/mxnet,indhub/mxnet,TuSimple/mxnet,indhub/mxnet,CodingCat/mxnet,ForkedReposBak/mxnet,tornadomeet/mxnet,eric-haibin-lin/mxnet,leezu/mxnet,rahul003/mxnet,mbaijal/incubator-mxnet,reminisce/mxnet,eric-haibin-lin/mxnet,TuSimple/mxnet,DickJC123/mxnet,mbaijal/incubator-mxnet,dmlc/mxnet,jiajiechen/mxnet,navrasio/mxnet,dmlc/mxnet,reminisce/mxnet,dmlc/mxnet,ptrendx/mxnet,larroy/mxnet,reminisce/mxnet,tlby/mxnet,leezu/mxnet,TuSimple/mxnet,jamesliu/mxnet,jamesliu/mxnet,CodingCat/mxnet,Northrend/mxnet,weleen/mxnet,navrasio/mxnet,LinkHS/incubator-mxnet,TuSimple/mxnet,tornadomeet/mxnet,tornadomeet/mxnet,zhreshold/mxnet,jamesliu/mxnet,zhreshold/mxnet,vikingMei/mxnet,yajiedesign/mxnet,larroy/mxnet,szha/mxnet,jamesliu/mxnet,sxjscience/mxnet,luoyetx/mxnet,tlby/mxnet,LinkHS/incubator-mxnet,LinkHS/incubator-mxnet,luoyetx/mxnet,szha/mxnet,leezu/mxnet,precedenceguo/mxnet,tlby/mxnet,dmlc/mxnet,luoyetx/mxnet,leezu/mxnet,rahul003/mxnet,TuSimple/mxnet,ptrendx/mxnet,LinkHS/incubator-mxnet,jamesliu/mxnet,jiajiechen/mxnet,mbaijal/incubator-mxnet,indhub/mxnet,szha/mxnet,eric-haibin-lin/mxnet,tlby/mxnet,rahul003/mxnet,ptrendx/mxnet,precedenceguo/mxnet,precedenceguo/mxnet,indhub/mxnet,ForkedReposBak/mxnet,indhub/mxnet,larroy/mxnet,tornadomeet/mxnet,TuSimple/mxnet,navrasio/mxnet,vikingMei/mxnet,luoyetx/mxnet,Northrend/mxnet,dmlc/mxnet,jiajiechen/mxnet,luoyetx/mxnet,vikingMei/mxnet,Northrend/mxnet,yajiedesign/mxnet,LinkHS/incubator-mxnet,apache/incubator-mxnet,zhreshold/mxnet,ForkedReposBak/mxnet,vikingMei/mxnet,larroy/mxnet,ptrendx/mxnet,LinkHS/incubator-mxnet,sxjscience/mxnet,weleen/mxnet,Northrend/mxnet,rahul003/mxnet,navrasio/mxnet,indhub/mxnet,zhreshold/mxnet,DickJC123/mxnet