glapi: Fix OpenGL ES 1.1 and 2.0 interop.

glapi: Fix OpenGL ES 1.1 and 2.0 interop.

Move _glapi_* symbols from libGLESv1_CM.so and libGLESv2.so to
libglapi.so.  This makes sure an app will get only one copy of glapi in
its address space.

Note that with this change, libGLES* and libglapi must be built from the
same source tree and distributed together.  This requirement comes from
the fact that the dispatch offsets used by these libraries are
re-assigned whenever GLAPI XMLs are changed.