Re: s/UNSPECIFIED/SIMPLE/ in foreign key code?

A small flaw in this plan is that in pg_constraint.confmatchtype,
MATCH_UNSPECIFIED is stored as 'u'.  In a green field I'd just rename
that to 's' for SIMPLE, but it seems possible that this would confuse
client-side code such as pg_dump or psql.  A quick look shows that
neither of those programs actually look directly at
pg_constraint.confmatchtype, instead relying on backend functions when
they want to deconstruct a foreign key constraint.  But there could well
be other client code that would notice the change.  So I'm a bit torn
as to whether to change it and create a release-note-worthy
compatibility issue, or to leave it as-is (with documentation notes that
"u" for MATCH_SIMPLE is a historical accident).

Thoughts?