I've also attached a revised version that makes IGNORE and RESPECT UNRESERVED keywords (following the pattern of NULLS_FIRST and NULLS_LAST).
Hm, you made another lookahead in base_yylex to make them unreserved -- looks ok, but not sure if there was no way to do it.
You might want to try byref types such as text. It seems you need to copy the datum to save the value in appropriate memory context. Also, try to create a view on those expressions. I don't think it correctly preserves it.