Add convenience.cc to src.mk
Add convenience.cc to src.mk

Summary:
The build process now requires new source files to be added to
src.mk. Adding convenience.cc to src.mk

Test Plan: Build rocksdb

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D34815

OverlordQ/rocksdb,facebook/rocksdb,tsheasha/rocksdb,lgscofield/rocksdb,wenduo/rocksdb,bbiao/rocksdb,IMCG/RcoksDB,SunguckLee/RocksDB,sorphi/rocksdb,jalexanderqed/rocksdb,Vaisman/rocksdb,tsheasha/rocksdb,siddhartharay007/rocksdb,kaschaeffer/rocksdb,IMCG/RcoksDB,flabby/rocksdb,ryneli/rocksdb,wskplho/rocksdb,vmx/rocksdb,alihalabyah/rocksdb,kaschaeffer/rocksdb,ryneli/rocksdb,IMCG/RcoksDB,vashstorm/rocksdb,JackLian/rocksdb,ryneli/rocksdb,hobinyoon/rocksdb,flabby/rocksdb,facebook/rocksdb,jalexanderqed/rocksdb,tsheasha/rocksdb,facebook/rocksdb,Vaisman/rocksdb,geraldoandradee/rocksdb,biddyweb/rocksdb,anagav/rocksdb,tizzybec/rocksdb,JoeWoo/rocksdb,kaschaeffer/rocksdb,siddhartharay007/rocksdb,alihalabyah/rocksdb,RyanTech/rocksdb,lgscofield/rocksdb,OverlordQ/rocksdb,geraldoandradee/rocksdb,Vaisman/rocksdb,SunguckLee/RocksDB,skunkwerks/rocksdb,fengshao0907/rocksdb,skunkwerks/rocksdb,temicai/rocksdb,wlqGit/rocksdb,anagav/rocksdb,temicai/rocksdb,Andymic/rocksdb,wskplho/rocksdb,geraldoandradee/rocksdb,wat-ze-hex/rocksdb,sorphi/rocksdb,zhangpng/rocksdb,Andymic/rocksdb,caijieming-baidu/rocksdb,caijieming-baidu/rocksdb,Applied-Duality/rocksdb,dkorolev/rocksdb,geraldoandradee/rocksdb,caijieming-baidu/rocksdb,sorphi/rocksdb,temicai/rocksdb,wat-ze-hex/rocksdb,alihalabyah/rocksdb,bbiao/rocksdb,makelivedotnet/rocksdb,JoeWoo/rocksdb,biddyweb/rocksdb,fengshao0907/rocksdb,alihalabyah/rocksdb,zhangpng/rocksdb,wskplho/rocksdb,hobinyoon/rocksdb,norton/rocksdb,amyvmiwei/rocksdb,hobinyoon/rocksdb,NickCis/rocksdb,sorphi/rocksdb,mbarbon/rocksdb,kaschaeffer/rocksdb,vashstorm/rocksdb,wskplho/rocksdb,Vaisman/rocksdb,tsheasha/rocksdb,vashstorm/rocksdb,facebook/rocksdb,JoeWoo/rocksdb,sorphi/rocksdb,bbiao/rocksdb,caijieming-baidu/rocksdb,wlqGit/rocksdb,dkorolev/rocksdb,OverlordQ/rocksdb,dkorolev/rocksdb,wat-ze-hex/rocksdb,ylong/rocksdb,tsheasha/rocksdb,caijieming-baidu/rocksdb,luckywhu/rocksdb,Andymic/rocksdb,anagav/rocksdb,wskplho/rocksdb,skunkwerks/rocksdb,alihalabyah/rocksdb,JohnPJenkins/rocksdb,ylong/rocksdb,wat-ze-hex/rocksdb,Vaisman/rocksdb,wenduo/rocksdb,bbiao/rocksdb,Applied-Duality/rocksdb,hobinyoon/rocksdb,vmx/rocksdb,temicai/rocksdb,IMCG/RcoksDB,NickCis/rocksdb,JackLian/rocksdb,fengshao0907/rocksdb,bbiao/rocksdb,ylong/rocksdb,vashstorm/rocksdb,Applied-Duality/rocksdb,temicai/rocksdb,Vaisman/rocksdb,makelivedotnet/rocksdb,norton/rocksdb,mbarbon/rocksdb,virtdb/rocksdb,wlqGit/rocksdb,makelivedotnet/rocksdb,IMCG/RcoksDB,virtdb/rocksdb,JohnPJenkins/rocksdb,RyanTech/rocksdb,geraldoandradee/rocksdb,vashstorm/rocksdb,SunguckLee/RocksDB,lgscofield/rocksdb,hobinyoon/rocksdb,tsheasha/rocksdb,luckywhu/rocksdb,jalexanderqed/rocksdb,makelivedotnet/rocksdb,JackLian/rocksdb,amyvmiwei/rocksdb,biddyweb/rocksdb,virtdb/rocksdb,makelivedotnet/rocksdb,NickCis/rocksdb,wenduo/rocksdb,dkorolev/rocksdb,luckywhu/rocksdb,norton/rocksdb,wlqGit/rocksdb,RyanTech/rocksdb,biddyweb/rocksdb,siddhartharay007/rocksdb,NickCis/rocksdb,OverlordQ/rocksdb,ryneli/rocksdb,rDSN-Projects/rocksdb.replicated,OverlordQ/rocksdb,hobinyoon/rocksdb,rDSN-Projects/rocksdb.replicated,siddhartharay007/rocksdb,hobinyoon/rocksdb,anagav/rocksdb,makelivedotnet/rocksdb,vmx/rocksdb,RyanTech/rocksdb,ylong/rocksdb,jalexanderqed/rocksdb,wlqGit/rocksdb,JohnPJenkins/rocksdb,JoeWoo/rocksdb,sorphi/rocksdb,mbarbon/rocksdb,dkorolev/rocksdb,rDSN-Projects/rocksdb.replicated,caijieming-baidu/rocksdb,wat-ze-hex/rocksdb,wlqGit/rocksdb,skunkwerks/rocksdb,bbiao/rocksdb,luckywhu/rocksdb,bbiao/rocksdb,rDSN-Projects/rocksdb.replicated,siddhartharay007/rocksdb,facebook/rocksdb,tizzybec/rocksdb,SunguckLee/RocksDB,Applied-Duality/rocksdb,norton/rocksdb,facebook/rocksdb,Andymic/rocksdb,tizzybec/rocksdb,geraldoandradee/rocksdb,amyvmiwei/rocksdb,geraldoandradee/rocksdb,rDSN-Projects/rocksdb.replicated,biddyweb/rocksdb,siddhartharay007/rocksdb,virtdb/rocksdb,kaschaeffer/rocksdb,JackLian/rocksdb,ryneli/rocksdb,SunguckLee/RocksDB,wenduo/rocksdb,anagav/rocksdb,wskplho/rocksdb,OverlordQ/rocksdb,Andymic/rocksdb,fengshao0907/rocksdb,JoeWoo/rocksdb,flabby/rocksdb,wat-ze-hex/rocksdb,mbarbon/rocksdb,flabby/rocksdb,JoeWoo/rocksdb,RyanTech/rocksdb,fengshao0907/rocksdb,vmx/rocksdb,Andymic/rocksdb,flabby/rocksdb,zhangpng/rocksdb,amyvmiwei/rocksdb,flabby/rocksdb,facebook/rocksdb,skunkwerks/rocksdb,Vaisman/rocksdb,fengshao0907/rocksdb,facebook/rocksdb,NickCis/rocksdb,wskplho/rocksdb,fengshao0907/rocksdb,tizzybec/rocksdb,ryneli/rocksdb,kaschaeffer/rocksdb,JackLian/rocksdb,wat-ze-hex/rocksdb,virtdb/rocksdb,skunkwerks/rocksdb,lgscofield/rocksdb,SunguckLee/RocksDB,OverlordQ/rocksdb,siddhartharay007/rocksdb,NickCis/rocksdb,wat-ze-hex/rocksdb,luckywhu/rocksdb,norton/rocksdb,tizzybec/rocksdb,ylong/rocksdb,norton/rocksdb,lgscofield/rocksdb,luckywhu/rocksdb,rDSN-Projects/rocksdb.replicated,IMCG/RcoksDB,amyvmiwei/rocksdb,lgscofield/rocksdb,hobinyoon/rocksdb,mbarbon/rocksdb,tizzybec/rocksdb,RyanTech/rocksdb,JohnPJenkins/rocksdb,jalexanderqed/rocksdb,makelivedotnet/rocksdb,JoeWoo/rocksdb,alihalabyah/rocksdb,kaschaeffer/rocksdb,ylong/rocksdb,zhangpng/rocksdb,dkorolev/rocksdb,Applied-Duality/rocksdb,wenduo/rocksdb,amyvmiwei/rocksdb,vmx/rocksdb,anagav/rocksdb,amyvmiwei/rocksdb,tizzybec/rocksdb,SunguckLee/RocksDB,vmx/rocksdb,anagav/rocksdb,Applied-Duality/rocksdb,IMCG/RcoksDB,jalexanderqed/rocksdb,mbarbon/rocksdb,norton/rocksdb,zhangpng/rocksdb,tsheasha/rocksdb,sorphi/rocksdb,lgscofield/rocksdb,tsheasha/rocksdb,wlqGit/rocksdb,vashstorm/rocksdb,SunguckLee/RocksDB,temicai/rocksdb,JohnPJenkins/rocksdb,JackLian/rocksdb,biddyweb/rocksdb,bbiao/rocksdb,zhangpng/rocksdb,jalexanderqed/rocksdb,wenduo/rocksdb,Andymic/rocksdb,rDSN-Projects/rocksdb.replicated,skunkwerks/rocksdb,temicai/rocksdb,mbarbon/rocksdb,vmx/rocksdb,JohnPJenkins/rocksdb,wenduo/rocksdb,norton/rocksdb,dkorolev/rocksdb,biddyweb/rocksdb,JohnPJenkins/rocksdb,virtdb/rocksdb,wenduo/rocksdb,JackLian/rocksdb,luckywhu/rocksdb,vmx/rocksdb,alihalabyah/rocksdb,vashstorm/rocksdb,virtdb/rocksdb,flabby/rocksdb,zhangpng/rocksdb,ylong/rocksdb,RyanTech/rocksdb,Andymic/rocksdb,caijieming-baidu/rocksdb,ryneli/rocksdb,Applied-Duality/rocksdb,NickCis/rocksdb