After the previous commit, several ES 2.0 functions would refer to
enums found in ES 3.0. These enums have been copied to ES 2.0, either
as core enums or as extensions.
ES 3.0 includes ES 2.0 verbatim. We can significantly reduce
duplication by using the same <replace> node for both APIs. Note that
the enumerations must remain separate, as ES 2.0 and 3.0 support
different tokens.
The <overload> element simplifies the addition of overloads for
backwards compatibility. It is defined similar to the <replace>
element, but instead of replacing the parameters of a function
in-place, it adds a new overload and modifies the overload instead.
Added strongly-typed enums for sections: Vertices, Shaders and
Programs. Added a number of missing enums for ES 2.0. Normalized
several APIs between OpenGL and OpenGL ES.
