pgsql: Doc: alphabetize the regexp_foo() function descriptions in 9.7.3

Doc: alphabetize the regexp_foo() function descriptions in 9.7.3.

For no visible reason (other than historical accident no doubt),
regexp_replace() was out of order. Re-order to match the way
that these functions are listed in 9.4. (That means substring()
remains first, because it's SQL-standard and the rest aren't.)
I've not touched the text other than to move it. This is just
to reduce confusion in the diffs for upcoming additions.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/64a1f225654f8866422010ff28e0d3384ae4c3af

Modified Files
--------------
doc/src/sgml/func.sgml | 86 +++++++++++++++++++++++++-------------------------
1 file changed, 43 insertions(+), 43 deletions(-)