Khan/khan-exercises — pull request #71287 by theinternetftw (2013-09-05 18:02:32+00:00)
Title: Fixes for rendering angles and quads

Several changes aimed at drawing quads correctly in the exercises that use them. So it's about fixing:

Overlapping angle labels (#68799)
Them (rarely) getting drawn partly off-screen (discovered while fixing the above)
And a general fix for all angles, where obtuse angles around 155 degrees would clip into the closest lines.