glsl2: Free the shader compiler at dri screen destruction.

Hooray, we can valgrind again without adding suppressions.  This also
adds an interface for use by an implementation of
glReleaseShaderCompiler().

src/glsl/glsl_parser_extras.cpp

@@ -741,3 +741,33 @@ do_common_optimization(exec_list *ir, bool linked)
 
    return progress;
 }
+
+extern "C" {
+
+/**
+ * To be called at GL teardown time, this frees compiler datastructures.
+ *
+ * After calling this, any previously compiled shaders and shader
+ * programs would be invalid.  So this should happen at approximately
+ * program exit.
+ */
+void
+_mesa_destroy_shader_compiler(void)
+{
+   _mesa_destroy_shader_compiler_caches();
+
+   _mesa_glsl_release_types();
+}
+
+/**
+ * Releases compiler caches to trade off performance for memory.
+ *
+ * Intended to be used with glReleaseShaderCompiler().
+ */
+void
+_mesa_destroy_shader_compiler_caches(void)
+{
+   _mesa_glsl_release_functions();
+}
+
+}

src/glsl/glsl_parser_extras.h

@@ -178,6 +178,9 @@ extern void _mesa_glsl_warning(const YYLTYPE *locp,
 extern "C" {
 extern int preprocess(void *ctx, const char **shader, char **info_log,
 		      const struct gl_extensions *extensions);
+
+extern void _mesa_destroy_shader_compiler();
+extern void _mesa_destroy_shader_compiler_caches();
 }
 
 extern void _mesa_glsl_lexer_ctor(struct _mesa_glsl_parse_state *state,

src/mesa/drivers/dri/common/dri_util.c

@@ -707,6 +707,8 @@ static void driDestroyScreen(__DRIscreen *psp)
 	 * stream open to the X-server anymore.
 	 */
 
+       _mesa_destroy_shader_compiler();
+
 	if (psp->DriverAPI.DestroyScreen)
 	    (*psp->DriverAPI.DestroyScreen)(psp);