Fixed crash on monitor disconnection.
Clarified language for file drop callback.
Aligned libGL soname to Linux ABI.

Fixed #261.
Formatting.
Added glfwGetWindowFrameSize.
Added use of frame size to multi-window test.
Formatting.
Added support for _NET_REQUEST_FRAME_EXTENTS.
Formatting.
Split out TLS code into separate modules.

This allows the TLS code to be re-used by partial ports like EGL.
Formatting.
Included extended flag in Win32 scan code.
Merge remote-tracking branch 'upstream/master'