fix missing _rotl64 symbol on Visual C 2003

Due to a bug in the CRT (msvcr71.dll), these 2 functions are not defined
in any lib Perl can use (static link CRTs dont apply, Perl only uses DLL
CRTs), but they are available as intrinsics. This solves a link error
about missing symbol __rotl64 in hv.obj, from usage in hv_func.h, on 32 bit
USE_64_BIT_INT VC 2003 builds. _rotr64 is included for completeness. This
fix is filed as [perl #120925].