glsl: add ir_emit_vertex and ir_end_primitive instruction types

These correspond to the EmitVertex and EndPrimitive functions in GLSL.

v2 (Paul Berry <stereotype441@gmail.com>): Add stub implementations of
new pure visitor functions to i965's vec4_visitor and fs_visitor
classes.

v3 (Paul Berry <stereotype441@gmail.com>): Rename classes to be more
consistent with the names used in the GL spec.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/ir_print_visitor.cpp

@@ -539,3 +539,15 @@ ir_print_visitor::visit(ir_loop_jump *ir)
 {
    printf("%s", ir->is_break() ? "break" : "continue");
 }
+
+void
+ir_print_visitor::visit(ir_emit_vertex *ir)
+{
+   printf("(emit-vertex)");
+}
+
+void
+ir_print_visitor::visit(ir_end_primitive *ir)
+{
+   printf("(end-primitive)");
+}