TINYGL: glBlendFunc Implementation

This pull request contains all the code for the task "implementing an openGL compliant version of the function glBlendFunc".
As I got build problems when just changing out your branch, it seems the change to modules.mk isn't part of this branch. But it's just a matter of a fixup or a squash. For now, to avoid doing a rebase at this point (which would delete the comments on github), just commit the module.mk-fix (and only that) as a new commit, we'll rebase it into place later.