Add shader program selection shortcut

Add a key manipulation that makes black text/paths use the standard
simple bitmap/patch shader, since they are the same. Previously we'd
create a separate shader for each because the keys differed, even
though the shaders were functionally equivalent.

Also fixes some issues around setting DEBUG_PROGRAM

Change-Id: I0c77c684d58da03501ee9ab8239c7d4a70fd6b5c