pgsql: Fix regex, LIKE, and some other second-rank text-manipulation

Log Message:
-----------
Fix regex, LIKE, and some other second-rank text-manipulation functions
to not cause needless copying of text datums that have 1-byte headers.
Greg Stark, in response to performance gripe from Guillaume Smet and
ITAGAKI Takahiro.

Modified Files:
--------------
    pgsql/src/backend/access/hash:
        hashfunc.c (r1.52 -> r1.53)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashfunc.c?r1=1.52&r2=1.53)
    pgsql/src/backend/utils/adt:
        like.c (r1.69 -> r1.70)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/like.c?r1=1.69&r2=1.70)
        like_match.c (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/like_match.c?r1=1.16&r2=1.17)
        oracle_compat.c (r1.71 -> r1.72)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/oracle_compat.c?r1=1.71&r2=1.72)
        regexp.c (r1.73 -> r1.74)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/regexp.c?r1=1.73&r2=1.74)
    pgsql/src/include:
        fmgr.h (r1.52 -> r1.53)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/fmgr.h?r1=1.52&r2=1.53)