[AD] shaders + ttf

[Jon Rafkind <workmin@xxxxxxxxxx>]

There seems to be an issue using the programmable pipeline and the ttf addon. Fonts sometimes don't draw, specifically when they are drawn to FBO's. Adding the following line to ttf.c:172 makes it work again, but I am unsure why. One possible reason is the upload of the page bitmap requires a shader, but Siegelord seems to suggest that isn't the case.

push_new_page:
   ...
   page = al_create_bitmap(256, 256);
+ page->shader = al_get_target_bitmap()->shader;

I'll try to make a test case showing the broken behavior.