More fixes for 64-bit systems

SystemInfo.pm:
- Use GlobalMemoryStatusEx instead of GlobalMemoryStatus.
- Update struct used by GetSystemInfo.
- Update comment about $proc_type.
test.pl
- Fix ProcessorInfo test (return value isn't always numeric).
example.pl
- Add example.pl script.

I've tested it on Strawberry Perl 5.16.2.1 64-bit using Win32::API 0.65 and 0.75.