mesa: Allow sampling from units >= MAX_TEXTURE_UNITS in shaders.

The total number of units used by a shader is limited to MAX_TEXTURE_UNITS,
but the actual indices are only limited by MAX_COMBINED_TEXTURE_IMAGE_UNITS,
since they're shared between vertex and fragment shaders.

NOTE: This is a candidate for the 7.11 branch.

Signed-off-by: Henri Verbeet <hverbeet@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/main/shaderapi.c

@@ -1032,7 +1032,7 @@ validate_samplers(const struct gl_program *prog, char *errMsg)
       "TEXTURE_2D",
       "TEXTURE_1D",
    };
-   GLint targetUsed[MAX_TEXTURE_IMAGE_UNITS];
+   GLint targetUsed[MAX_COMBINED_TEXTURE_IMAGE_UNITS];
    GLbitfield samplersUsed = prog->SamplersUsed;
    GLuint i;