Glaze: A thin, flexible layer for wrapping OpenGL

Glaze is a very thin layer intended to assist developers of
OpenGL-wrapping libraries. The result of compiling Glaze is a tiny
libGL.so library with a symbol for every possible GL and GLX function
in the OpenGL API.

Each symbol within the Glaze library is merely an "ifunc resolver"[*]
which will resolve to a function in the wrapper library if one exists,
or will otherwise resolve to a function in the underlying "real"
OpenGL library.

In order to use glaze, the following three environment variables
should be set:

    LD_LIBRARY_PATH

	This should be set so that the directory containing Glaze's
	libGL.so appears on the list earlier than any other OpenGL
	library implementation. For example:

	    LD_LIBRARY_PATH=/home/user/src/glaze/lib64:${LD_LIBRARY_PATH}

    GLAZE_WRAPPER

	This should be set to the complete path to the library
	containing some OpenGL wrapper functions. These functions must
	manually call into the underlying OpenGL functions as
	needed. An example of setting this variable is:

	    GLAZE_WRAPPER=/home/user/src/mywrapper/libGL.so

    GLAZE_LIBGL

	This should be set to the complete path to the "real",
	underlying OpengL library implementation. For example:

	    GLAZE_LIBGL=/usr/lib/libGL.so

For any questions or comments about Glaze, please feel free to email
me:

	Carl Worth <cworth@cworth.org>

Credits: Many thanks to Alexander Monakov who gave me the idea for
using "ifunc resolvers" for efficient wrapping of OpenGL functions,
(and for patiently teaching me how they work). See Alexander's
project, Primus, for the inspiration for Glaze:
https://github.com/amonakov/primus

[*] An "ifunc resolver" is a glibc mechanism for performing efficent,
one-shot function resolutions. The first call to the function will
invoke the resolver which has the job of returning the "real" function
to call. At that point, the application PLTs will be updated with the
returned function pointer so that all future calls will call the
desired function without any subsequent overhead.