glsl2: Make the dead code handler make its own talloc context.

This way, we don't need to pass in a parse state, and the context
doesn't grow with the number of passes through optimization.

src/glsl/main.cpp

@@ -162,7 +162,7 @@ compile_shader(struct gl_shader *shader)
 	 progress = do_if_simplification(shader->ir) || progress;
 	 progress = do_copy_propagation(shader->ir) || progress;
 	 progress = do_dead_code_local(shader->ir) || progress;
-	 progress = do_dead_code_unlinked(state, shader->ir) || progress;
+	 progress = do_dead_code_unlinked(shader->ir) || progress;
 	 progress = do_constant_variable_unlinked(shader->ir) || progress;
 	 progress = do_constant_folding(shader->ir) || progress;
 	 progress = do_algebraic(shader->ir) || progress;