Implement LIKE/ESCAPE. Change parser to use like()/notlike()

Implement LIKE/ESCAPE. Change parser to use like()/notlike()
 rather than the "~~" operator; this made it easy to add ESCAPE features.
Implement ILIKE, NOT ILIKE, and the ESCAPE clause for them.
 afaict this is not MultiByte clean, but lots of other stuff isn't either.
Fix up underlying support code for LIKE/NOT LIKE.
 Things should be faster and does not require internal string copying.
Update regression test to add explicit checks for
 LIKE/NOT LIKE/ILIKE/NOT ILIKE.
Remove colon and semi-colon operators as threatened in 7.0.
Implement SQL99 COMMIT/AND NO CHAIN.
 Throw elog(ERROR) on COMMIT/AND CHAIN per spec
 since we don't yet support it.
Implement SQL99 CREATE/DROP SCHEMA as equivalent to CREATE DATABASE.
 This is only a stopgap or demo since schemas will have another
 implementation soon.
Remove a few unused production rules to get rid of warnings
 which crept in on the last commit.
Fix up tabbing in some places by removing embedded spaces.