Update me7sum.c

Fixes 2 issues preventing compilation under Win32 Mingw environment.
1. GetRomInfo was broken, work around was to pass property value to rom info function.
2. %z unsupported on my platform so changed to %ld and cast to long integer which should be sufficient for this purpose.

(Note: Win32 MinGW doesn't support 'mmap' (functions not found) so I added 'nman', an emulation files (see mman.c and .h), this adds these features and is only compiled for win32 targets.)