st/mesa: avoid exposing EXT_texture_integer for pre-GLSL 1.30
st/mesa: avoid exposing EXT_texture_integer for pre-GLSL 1.30

For drivers building up to GL(ES)3, only expose the actual extension if
the API will let it be used (e.g. via overrides/debug flags that enable
higher versions).

Signed-off-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>
Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler