Correct Map for file sizes larger than 1<<31 - 1
Correct Map for file sizes larger than 1<<31 - 1

int(int64value) doesn't always return <0 when an int is 32 bits.
Long ago, Go moved to 64 bit int's on amd64 and mmap-ing large files works fine.
Should not panic when an error return is the sane thing to do.
Remove un-used ANON (which should probably have been set to syscall.MAP_ANON anyway).
HouzuoGuo/tiedot,zj8487/tiedot,henrylee2cn/tiedot,henrylee2cn/tiedot,kylewolfe/tiedot,kylewolfe/tiedot,kylewolfe/tiedot,cresg820/tiedot,prods/tiedot,marbemac/tiedot,prods/tiedot,HouzuoGuo/tiedot,HouzuoGuo/tiedot,stoplightio/tiedot,cresg820/tiedot,stoplightio/tiedot,HouzuoGuo/tiedot,zj8487/tiedot,prods/tiedot,zj8487/tiedot,cresg820/tiedot,figoxu/tiedot,figoxu/tiedot,figoxu/tiedot,stoplightio/tiedot,henrylee2cn/tiedot,marbemac/tiedot,marbemac/tiedot