pgsql: Add built-in userlock manipulation functions to replace the

Log Message:
-----------
Add built-in userlock manipulation functions to replace the former
contrib functionality.  Along the way, remove the USER_LOCKS configuration
symbol, since it no longer makes any sense to try to compile that out.
No user documentation yet ... mmoncure has promised to write some.
Thanks to Abhijit Menon-Sen for creating a first draft to work from.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        catalogs.sgml (r2.132 -> r2.133)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.132&r2=2.133)
    pgsql/src/backend/storage/lmgr:
        README (r1.20 -> r1.21)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/README.diff?r1=1.20&r2=1.21)
        deadlock.c (r1.41 -> r1.42)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/deadlock.c.diff?r1=1.41&r2=1.42)
        lock.c (r1.172 -> r1.173)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/lock.c.diff?r1=1.172&r2=1.173)
    pgsql/src/backend/utils/adt:
        lockfuncs.c (r1.24 -> r1.25)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/lockfuncs.c.diff?r1=1.24&r2=1.25)
    pgsql/src/backend/utils/init:
        postinit.c (r1.169 -> r1.170)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/postinit.c.diff?r1=1.169&r2=1.170)
    pgsql/src/include/catalog:
        catversion.h (r1.357 -> r1.358)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.357&r2=1.358)
        pg_proc.h (r1.425 -> r1.426)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.425&r2=1.426)
    pgsql/src/include:
        pg_config_manual.h (r1.22 -> r1.23)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pg_config_manual.h.diff?r1=1.22&r2=1.23)
    pgsql/src/include/storage:
        lock.h (r1.98 -> r1.99)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/lock.h.diff?r1=1.98&r2=1.99)
    pgsql/src/include/utils:
        builtins.h (r1.281 -> r1.282)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h.diff?r1=1.281&r2=1.282)