Detect libnames with .so.<.digit>$ and use them unchanged.

This allows things like "is native('libncurses.so.5')" which would previously attempt to load libncurses.so.5.so.
Extend recognition of libraries with .so.<digit>+ to .so(.<digit>+)+

This allows calling libraries named like libfoo.so.1.2.2
Merge pull request #53 from mathw/master

Detect libnames with .so.<.digit>$ and use them unchanged.