Detect when the eagl surface changed its dimension (when the user rotates
the device for example) and adapt the egl internals to draw to that,
preventing that ios resizes the image again when drawing.
This is particularly harmful when eagl would scale down a image
to draw and the ios screen would scale it back up because the
surface is now bigger than when the element was configured.
It seems EAGL expects the application to simply ignore unused
EAGL contexts as the resources for it would be released when a new
context is set as the current one. Also move the egl extensions
querying to after a context is set to prevent crashes.
This makes the EAGL version of eglglessink reusable.
Put EGL specific code to a separate file and create the same functions
for EAGL, the Apple's specific EGL implementaton.
At this point, the EAGL version wasn't compiled or tested as there isn't
any simple documented way to build 1.0 for iOS. This code for the EAGL
version is still the 0.10 version, some updates should be made when 1.0
is buildable for iOS.
