Clean up the Windows x64 changes.

Clean up the Windows x64 changes.

 nt/preprep.c (RVA_TO_PTR): Use 'unsigned char *' instead of
 'void *', for pointer arithmetics.
 (OFFSET_TO_RVA, RVA_TO_OFFSET, RVA_TO_SECTION_OFFSET): Enclose all
 macro arguments in parentheses.

 src/unexw32.c (OFFSET_TO_RVA, RVA_TO_OFFSET)
 (RVA_TO_SECTION_OFFSET): Encode all macro arguments in parentheses.
 (RVA_TO_PTR): Cast the result of RVA_TO_OFFSET to 'unsigned char *',
 as the previous version used 'void *'.
 src/ralloc.c (ROUNDUP): Fix last change.
 (MEM_ROUNDUP): Don't cast MEM_ALIGN, it is already of type
 'size_t'.