Adds functions to find png files when pygame is used (optional for Python 2.7.11)

[opacam]

This PR has the words "optional for Python 2.7.11" to keep reference to the original PR #775 (Python 2.7.11).

[inclement]

I'm not clear what's going on with the `if 'pygame' in recipe_build_order' stuff - is this to do with a bootstrap/jni vs recipe build?

[opacam]

Yes, You are right, let me clarify this stuff: all the recipes that are dependent on png (I think that those are recipes: pil and pygame) are linked to the build of png's recipe, but, when using pygame bootstrap, the library inside the app is the one builded inside jni (that has different version from the one from recipe), that fact causes errors at runtime, because the distributed png's library is different from the one who we linked at build time (for pygame and pil). With this PR I force to link the mentioned recipes (pil, pygame) against the final library used in the app, this way we avoids errors at runtime.

This is a dependency for PRs: #786 and #787 (I mention in those posts but not here, sorry about that)

PD: At some point I tried to force the build of png's recipe instead of the one distributed inside the "pygame_boostrap_components", as I do in PR #787, but unfortunately, the newer version missed some function that prevents the build...so... we must stick with the old version distributed with "pygame_boostrap_components"

NOTE: @inclement...be careful with this PR (and all the PRs with python-2.7.11 in his title) because is not tested against the old recipes...all my test are against the new pytyhon 2.7.11 (PR #775) and all his manadatory and optional PRs, but maybe it will work with the current recipes: python2, pil pygame,pygame_boostrap_components....
I thought about a big PR #693, and at some point, the user @kived, notices that it was very difficult to review all the changes so I tried to split all the initial PR into little pieces to make it easy to review/test.

[opacam]

¡¡¡ Closed because currently I'm working with python's version 2.7.12,
and this recipe isn't needed anymore !!!