Formerly, we required that the OpenGL mode was fixed at compile time. Now we
allow the code to work with whatever it is given at runtime.
It is still possible to force a context type on compile time.
Formerly we relied on static linkage. However, in the presense of modern
OpenGL (ES) implementations it is not easily identifable which library to link
against. For example, on Linux amd64 with nVidia drivers and SDL2 setup to
create a GLES 1.1 context one would need to link against libGL.so. However,
traditionally GLES 1.1 required to link against libGLESv1_CM.so. To prevent a
huge mess we simply resolve the OpenGL functions on run-time now and stop
linking against a static library (in most cases).
GLES support needs to be enabled manually on configure time for now.
Tizen changes have NOT been tested.
