pgsql: Mark to_number() and the numeric-type variants of to_char() as

Log Message:
-----------
Mark to_number() and the numeric-type variants of to_char() as stable, not
immutable, because their results depend on lc_numeric; this is a longstanding
oversight.  We cannot force initdb for this in the back branches, but we can
at least provide correct catalog entries for future installations.

Tags:
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REL8_0_STABLE

Modified Files:
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    pgsql/src/include/catalog:
        pg_proc.h (r1.349 -> r1.349.4.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.349&r2=1.349.4.1)