glsl: Track whether uniforms are active per stage

for finer granularity state flagging

v2: Marek - use a bitmask, add shader cache support

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/compiler/glsl/ir_uniform.h

@@ -106,6 +106,11 @@ struct gl_uniform_storage {
 
    struct gl_opaque_uniform_index opaque[MESA_SHADER_STAGES];
 
+   /**
+    * Mask of shader stages (1 << MESA_SHADER_xxx) where this uniform is used.
+    */
+   unsigned active_shader_mask;
+
    /**
     * Storage used by the driver for the uniform
     */