crc32: build a whole special Extend function for SSE 4.2.
crc32: build a whole special Extend function for SSE 4.2.

Disassembling the Extend function shows something that looks
much more healthy now. The SSE 4.2 instructions are right
there in the body of the function.

Intel(R) Core(TM) i7-3540M CPU @ 3.00GHz

Before:

crc32c: 1.305 micros/op 766260 ops/sec; 2993.2 MB/s (4K per op)

After:

crc32c: 0.442 micros/op 2263843 ops/sec; 8843.1 MB/s (4K per op)

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