Load program binary extension on Linux
Fix rebase
Merge pull request #698 from mapbox/cache-shaders

Add caching of compiled shaders
Remove Map::cleanup and Painter::cleanup

Both were noops.
add user agent header

fixes #628
Merge pull request #628 from mapbox/user-agents

Set user agent to something useful
wrap mbgl-core and mbgl-linux in -Wl,--start-group/-Wl,--end-group
only group on linux
disable uv_thread_self() asserts, ref #623