Squashed 'libs/EXTERNAL/libezgl/' changes from 172bcb4..e6f62b3

e6f62b3 enable saving graphics without getting into the event loop (#11)
5243fa0 Merge pull request #12 from mariobadr/fix-warnings
45e4bba fix more warning messages in graphics.cpp and canvas.cpp
17557e4 change variable names in rectangle.hpp to avoid shallowing warnings

git-subtree-dir: libs/EXTERNAL/libezgl
git-subtree-split: e6f62b3a4f88bd523a8b77af1494839f83f62bc7