Fix incompatibilities with 64-bit Windows builds.

Fix incompatibilities with 64-bit Windows builds.

 src/w32fns.c (cache_system_info): Cast sysinfo_cache.dwPageSize to
 DWORD_PTR, for compatibility with 64-bit builds.
 src/w32.c (_PROCESS_MEMORY_COUNTERS_EX):
 (GetProcessWorkingSetSize_Proc, get_process_working_set_size)
 (system_process_attributes): Use SIZE_T rather than DWORD, for
 compatibility with 64-bit builds.