weston.man: Document the way to disable idle timeout
Revert "weston.ini: Use 'modeline' key for modeline example"

This reverts commit 97a56145636316fdb431b91ec64adff217287cd9.

The current code detects the mode key, not modeline. Reference:
http://cgit.freedesktop.org/wayland/weston/tree/src/compositor-drm.c#n2464
weston-egl: Allow compilation against older EGL stack

Provide a definition of EGL_BUFFER_AGE_EXT so that you can compile against an
EGL stack that may not yet support that extension.