Improve handle_mw_command argument handling:

- Change: All local variable types are now unsigned.
- Use parse_u32 to ensure address and value parse properly.
- Use parse_uint to ensure count parses properly.
- Move variables to location of first use.


git-svn-id: svn://svn.berlios.de/openocd/trunk@2231 b42882b7-edfa-0310-969c-e2dbd0fdcd60