mesa-demos: Use PACKAGECONFIG to enable/disable features

mesa-demos: Use PACKAGECONFIG to enable/disable features

This allow selection of following features:

 drm, egl, freetype2, gbm, gles1, gles2, glut, osmesa, vg, wayland, x11

The x11 features is enabled depending on distro features but the
wayland has not been enabled as it does not work with Wayland
1.0. Rest were enabled for a sane default.

(From OE-Core rev: dc2de313febfc817640e4e55c75d0cb21c70c0ba)

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>