Fix compilation on Linux kernels or glibc versions lacking sync_file_range().
Fix compilation on Linux kernels or glibc versions lacking sync_file_range().

This fixes issue #667.

Many thanks to Didier Spezia for the fix.

janeasystems/redis,damy/redis,ideaar/redis,Jonavin/redis,alpha8/redis,ideaar/redis,jqk6/redis,adamweixuan/redis,kolonse/redis,sidsen/redis,jqk6/redis,hanmichael/redis,alpha8/redis,upsoft/redis,jaambee/redis,quangnguyen90/redis,kolonse/redis,Cybermaxs/redis,Cybermaxs/redis,nandhanurrevanth/redis,janeasystems/redis,kts12345/redis,jaambee/redis,Cybermaxs/redis,kts12345/redis,Cybermaxs/redis,ideaar/redis,ScottKaiGu/redis,DeNA/redis,oaastest/redis,jqk6/redis,kts12345/redis,DeNA/redis,enginekit/redis,miminus/redis,oaastest/redis,shanegxxiao/redis,laurencee/redis,liqiang199105/redis,adamweixuan/redis,hanmichael/redis,daogangtang/redis_luajit2.6,enginekit/redis,miminus/redis,grisha/thredis,Cybermaxs/redis,shanegxxiao/redis,jqk6/redis,quangnguyen90/redis,jaambee/redis,adamweixuan/redis,nandhanurrevanth/redis,sidsen/redis,upsoft/redis,laurencee/redis,janeasystems/redis,liqiang199105/redis,upsoft/redis,kts12345/redis,alpha8/redis,Jonavin/redis,sidsen/redis,shanegxxiao/redis,kolonse/redis,grisha/thredis,jaambee/redis,Jonavin/redis,oaastest/redis,ScottKaiGu/redis,grisha/thredis,ScottKaiGu/redis,jacklee0810/redis,daogangtang/redis_luajit2.6,oaastest/redis,janeasystems/redis,laurencee/redis,kts12345/redis,daogangtang/redis_luajit2.6,nandhanurrevanth/redis,janeasystems/redis,DeNA/redis,enginekit/redis,grisha/thredis,jacklee0810/redis,ideaar/redis,hanmichael/redis,enginekit/redis,jqk6/redis,sidsen/redis,damy/redis,upsoft/redis,miminus/redis,jacklee0810/redis,adamweixuan/redis,jaambee/redis,alpha8/redis,shanegxxiao/redis,ScottKaiGu/redis,kolonse/redis,adamweixuan/redis,nandhanurrevanth/redis,oaastest/redis,ScottKaiGu/redis,quangnguyen90/redis,damy/redis,nandhanurrevanth/redis,hanmichael/redis,daogangtang/redis_luajit2.6,hanmichael/redis,miminus/redis,Jonavin/redis,alpha8/redis,ideaar/redis,laurencee/redis,enginekit/redis,Jonavin/redis,jacklee0810/redis,sidsen/redis,jacklee0810/redis,shanegxxiao/redis,quangnguyen90/redis,sidsen/redis,damy/redis,liqiang199105/redis,upsoft/redis,liqiang199105/redis,quangnguyen90/redis,kolonse/redis,liqiang199105/redis,damy/redis,miminus/redis,laurencee/redis