Adding a couple of useful methods:
Adding a couple of useful methods:

- render font.Label to texture using FBO (can't implement using AUX-and-copy
  'cos I can't seem to get that working here)
- calculate width of slice of font.Label

mpasternak/pyglet-fix-issue-518-522,cledio66/pyglet,arifgursel/pyglet,mpasternak/pyglet-fix-issue-518-522,Austin503/pyglet,odyaka341/pyglet,odyaka341/pyglet,odyaka341/pyglet,shaileshgoogler/pyglet,qbektrix/pyglet,mpasternak/pyglet-fix-issue-552,mpasternak/pyglet-fix-issue-518-522,odyaka341/pyglet,mpasternak/pyglet-fix-issue-552,xshotD/pyglet,gdkar/pyglet,odyaka341/pyglet,Austin503/pyglet,xshotD/pyglet,arifgursel/pyglet,google-code-export/pyglet,shaileshgoogler/pyglet,mpasternak/michaldtz-fixes-518-522,Austin503/pyglet,cledio66/pyglet,mpasternak/michaldtz-fix-552,google-code-export/pyglet,shaileshgoogler/pyglet,Alwnikrotikz/pyglet,kmonsoor/pyglet,gdkar/pyglet,google-code-export/pyglet,xshotD/pyglet,Alwnikrotikz/pyglet,google-code-export/pyglet,mpasternak/pyglet-fix-issue-518-522,gdkar/pyglet,kmonsoor/pyglet,kmonsoor/pyglet,mpasternak/michaldtz-fixes-518-522,mpasternak/michaldtz-fix-552,cledio66/pyglet,qbektrix/pyglet,gdkar/pyglet,mpasternak/michaldtz-fixes-518-522,cledio66/pyglet,shaileshgoogler/pyglet,Alwnikrotikz/pyglet,kmonsoor/pyglet,xshotD/pyglet,arifgursel/pyglet,mpasternak/michaldtz-fix-552,Austin503/pyglet,mpasternak/pyglet-fix-issue-552,qbektrix/pyglet,google-code-export/pyglet,qbektrix/pyglet,xshotD/pyglet,mpasternak/michaldtz-fix-552,shaileshgoogler/pyglet,mpasternak/michaldtz-fixes-518-522,qbektrix/pyglet,gdkar/pyglet,arifgursel/pyglet,arifgursel/pyglet,mpasternak/pyglet-fix-issue-552,kmonsoor/pyglet,Alwnikrotikz/pyglet,Alwnikrotikz/pyglet,Austin503/pyglet,cledio66/pyglet