Use long for rehash and iterator index in dict.h.
Use long for rehash and iterator index in dict.h.

This allows to support datasets with more than 2 billion of keys
(possible in very large memory instances, this bug was actually
reported).

Closes issue #1814.

jacklee0810/redis,ideaar/redis,hanmichael/redis,ScottKaiGu/redis,upsoft/redis,enginekit/redis,adamweixuan/redis,miminus/redis,ScottKaiGu/redis,upsoft/redis,liqiang199105/redis,enginekit/redis,damy/redis,liqiang199105/redis,LittlePeng/redis,ScottKaiGu/redis,damy/redis,jqk6/redis,shanegxxiao/redis,hanmichael/redis,jqk6/redis,StartTheShift/redis-shift,miminus/redis,alpha8/redis,hanmichael/redis,laurencee/redis,upsoft/redis,janeasystems/redis,LittlePeng/redis,liqiang199105/redis,kts12345/redis,laurencee/redis,enginekit/redis,jqk6/redis,laurencee/redis,jacklee0810/redis,jaambee/redis,sidsen/redis,kolonse/redis,quangnguyen90/redis,sidsen/redis,upsoft/redis,kts12345/redis,kolonse/redis,liqiang199105/redis,adamweixuan/redis,miminus/redis,jaambee/redis,Jonavin/redis,sidsen/redis,quangnguyen90/redis,kolonse/redis,ideaar/redis,shanegxxiao/redis,janeasystems/redis,adamweixuan/redis,ideaar/redis,Cybermaxs/redis,fanxu/redis,janeasystems/redis,quangnguyen90/redis,janeasystems/redis,shanegxxiao/redis,shanegxxiao/redis,ideaar/redis,hanmichael/redis,fanxu/redis,alpha8/redis,hanmichael/redis,Jonavin/redis,nandhanurrevanth/redis,fanxu/redis,jaambee/redis,kts12345/redis,enginekit/redis,kts12345/redis,kolonse/redis,Cybermaxs/redis,StartTheShift/redis-shift,fanxu/redis,damy/redis,Jonavin/redis,jqk6/redis,alpha8/redis,nandhanurrevanth/redis,laurencee/redis,ideaar/redis,nandhanurrevanth/redis,StartTheShift/redis-shift,kolonse/redis,quangnguyen90/redis,kts12345/redis,jacklee0810/redis,jaambee/redis,ScottKaiGu/redis,erwin00776/redis-2.8-optimize,sidsen/redis,jqk6/redis,laurencee/redis,alpha8/redis,jacklee0810/redis,Cybermaxs/redis,Cybermaxs/redis,Cybermaxs/redis,LittlePeng/redis,erwin00776/redis-2.8-optimize,enginekit/redis,sidsen/redis,erwin00776/redis-2.8-optimize,adamweixuan/redis,janeasystems/redis,shanegxxiao/redis,jaambee/redis,damy/redis,liqiang199105/redis,adamweixuan/redis,damy/redis,Jonavin/redis,alpha8/redis,jacklee0810/redis,sidsen/redis,nandhanurrevanth/redis,Jonavin/redis,nandhanurrevanth/redis,upsoft/redis,erwin00776/redis-2.8-optimize,miminus/redis,quangnguyen90/redis,miminus/redis,ScottKaiGu/redis