Add the ability to generate programs that doesn't use condition codes.

ctx->Shader.EmitCondCodes determines if we use condition codes.
If not, IF statement uses first operand's X component as the condition.
Added OPCODE_BRK0, OPCODE_BRK1, OPCODE_CONT0, OPCODE_CONT1 to handle
the common cases of conditional break/continue.
diff --git a/src/mesa/shader/shader_api.c b/src/mesa/shader/shader_api.c
index aab522e..88aa8c5 100644
--- a/src/mesa/shader/shader_api.c
+++ b/src/mesa/shader/shader_api.c
@@ -206,6 +206,7 @@
     * are generated by the GLSL compiler.
     */
    ctx->Shader.EmitHighLevelInstructions = GL_TRUE;
+   ctx->Shader.EmitCondCodes = GL_TRUE; /* XXX probably want GL_FALSE... */
    ctx->Shader.EmitComments = GL_FALSE;
 }