pgsql: Get rid of ParseState.p_value_substitute; use a columnref hook i

Get rid of ParseState.p_value_substitute; use a columnref hook instead.

I noticed that p_value_substitute, which is a single-purpose kluge I added
in 2002 (commit b0422b215), could be replaced by having domainAddConstraint
install a parser hook that looks for the name "value". The parser hook
code only dates back to 2009, so it's not surprising that we had to kluge
this in 2002, but we can do it more cleanly now.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/7c3abe3c92fd3a14a70bc2f888f936cd6fe28c0f

Modified Files
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src/backend/commands/typecmds.c | 34 +++++++++++++++++++++++++++++++++-
src/backend/parser/parse_expr.c | 21 ---------------------
src/include/parser/parse_node.h | 4 ----
3 files changed, 33 insertions(+), 26 deletions(-)