Re-implement libOpenGL such that ELF symbol filtering is optional

This implementation uses the same strategy as libGL to implement OpenGL
entrypoints.  The only difference between this library and libGL is
that the GLX wrapper functions are omitted.

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
Add a configure option to build libGL with ELF symbol filtering

This option is disabled by default due to glibc bug 16272.

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
Allow arguments to be passed to the configure script through dbg_configure.sh

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
Unifdef USE_MGL_NAMESPACE macro

This macro is unused by libglvnd.

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
Add missing _GNU_SOURCE define in libglx.c

This is needed to use the RTLD_DEFAULT pseudo-handle on x86 platforms.

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
[testglxmakecurrent] Initialize the window_info struct before possible failure

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
Update README now that ELF symbol filtering is disabled by default

Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>