GL3.txt: update softpipe ARB_gpu_shader5 status
GL3.txt: update softpipe ARB_gpu_shader5 status

texture gather and it already supported the new instructions.

Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler