Mark the functions 'exec="skip"' in the XML instead.  libGL will still
have the functions, but the driver won't try to use them.  I verified
that this commit works with piglit's 'object-namespace-pollution glClear
vertex-array' on x64 with a driver built from mesa-12.0.3 tag.

In fairness, this test also works with a libGL built from 7927d037

.  I
believe it continues to work because on non-Windows platforms we
generate some extra, dummy dispatch functions that can be used when a
driver requests a function unknown to libGL.  This was done to provide
some "forward" compatibility with drivers that need more functions.
This doesn't work on Windows because the Windows calling convention is
for the callee to clean up the stack.  That's the theory anyway.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>