Log Message:
Update ruby-inline to 3.12.0.

=== 3.12.0 / 2012-12-18

* 1 major enhancement:

  * map_ruby_const prefixes c-vars with 'c' (eg Name -> cName).

* 1 minor enhancement:

  * Added #add_id to make interning symbols in C clean and easy

=== 3.11.4 / 2012-11-23

* 1 minor enhancement:

  * Improve windows compatibility (MinGW). (luislavena)