glsl: Forbid non-constant image array indexing in GLSL ES 3.1.
glsl: Forbid non-constant image array indexing in GLSL ES 3.1.

Reviewed-by: Timothy Arceri <7f85c8176b2576ffafd04ac63cd29ed35ff86cb6@yahoo.com.au>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler