Fixed all EGLConfigs listed as single-buffered.

The commit c980858 added a new flag to _GLFWfbconfig that was not being
set by EGLConfig enumeration.  This patch assumes eglCreateWindowSurface
only creates double-buffered surfaces.

Fixes #315.
wayland: Fix indentation
wayland: Add basic input support
wayland: Build with -pthread
examples/boing: Add ball-follow-cursor functionality

Make it so that in the boing example, when the user clicks, the ball
follows the mouse cursor.
x11: Move KeySym to unicode converter out of x11 backend

To be used by the Wayland backend.
wayland: Add keyboard support

Adds libxkbcommon as a dependency when enabling the Wayland backend.
Merge pull request #316 from jadahl/wayland-input

Wayland input work.
Merge remote-tracking branch 'upstream/master'