pgsql: Fix erroneous handling of shared dependencies (ie dependencies on

Log Message:
-----------
Fix erroneous handling of shared dependencies (ie dependencies on roles)
in CREATE OR REPLACE FUNCTION.  The original code would update pg_shdepend
as if a new function was being created, even if it wasn't, with two bad
consequences: pg_shdepend might record the wrong owner for the function,
and any dependencies for roles mentioned in the function's ACL would be lost.
The fix is very easy: just don't touch pg_shdepend at all when doing a
function replacement.

Also update the CREATE FUNCTION reference page, which never explained
exactly what changes and doesn't change in a function replacement.
In passing, fix the CREATE VIEW reference page similarly; there's no
code bug there, but the docs didn't say what happens.

Modified Files:
--------------
    pgsql/doc/src/sgml/ref:
        create_function.sgml (r1.86 -> r1.87)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_function.sgml?r1=1.86&r2=1.87)
        create_view.sgml (r1.41 -> r1.42)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_view.sgml?r1=1.41&r2=1.42)
    pgsql/src/backend/catalog:
        pg_proc.c (r1.165 -> r1.166)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_proc.c?r1=1.165&r2=1.166)