pgsql: Add a useless return statement to suppress a warning seen with

Log Message:
-----------
Add a useless return statement to suppress a warning seen with some
versions of gcc (I'm seeing it with Apple's gcc 4.0.1). I think the
reason we did not see this before was that the assert() macros in the
regex code were all no-ops till recently.

Modified Files:
--------------
pgsql/src/backend/regex:
regc_lex.c (r1.5 -> r1.6)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/regex/regc_lex.c?r1=1.5&r2=1.6)