Portable proplib 0.5.1 released

A new version was released with the following changes:

• Added pkg-config support and install a proplib.pc file.
• Merged stuff from old subversion repo, that re-added the change to emit base 10 rather than base 16 for unsigned numbers contributed by Adam Hoka.

Please see http://code.google.com/p/portableproplib for more information.