2.12.5:

* Documentation:
  - Show stock icon images in the API reference again. 
  - Show some pictures of widgets in the API reference.
  (Jonathon Jongsma)

* Build:
  - Fix header inclusion and use using directive for C functions to
    fix build on gcc-4.3 (pre-releases) and Solaris. 
    (Deng Xiyue, Tim Mooney, Kjartan Maraas, Bug #498438, #517530)
  - Install and find all needed files for gtkmm-demo, and correct the 
    executable name.
    (Chris Wang. Bug #516602, #516600)