Mac OSX strings

Added in version 1.8.

Mac OSX .strings files are used for some Cocoa / Carbon application localization, such as for the iPhone, iPod, and OSX. They are somewhat similar to Java properties, and therefore prop2po and po2prop are used for conversion.

This format is standardized as PWG 5100.13 and used on NeXTSTEP/OpenSTEP as well.