Naive implementation of IF/ELSE/ENDIF.

Handle TGSI labels correctly.
Enhance MESA opcode info queries.
diff --git a/src/mesa/shader/prog_instruction.h b/src/mesa/shader/prog_instruction.h
index c800757..643969b 100644
--- a/src/mesa/shader/prog_instruction.h
+++ b/src/mesa/shader/prog_instruction.h
@@ -440,6 +440,9 @@
 extern GLuint
 _mesa_num_inst_src_regs(gl_inst_opcode opcode);
 
+extern GLuint
+_mesa_num_inst_dst_regs(gl_inst_opcode opcode);
+
 extern const char *
 _mesa_opcode_string(gl_inst_opcode opcode);