Start of Framebuffer based rendering

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Add frame_size signal

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Add configure for glext.h

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Tidy up default frame buffer creation

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>