pgsql: Add pg_conf_load_time() function to report when the Postgres

[tgl(at)postgresql(dot)org (Tom Lane)]

Log Message:
-----------
Add pg_conf_load_time() function to report when the Postgres configuration
files were last loaded.

George Gensure

Modified Files:
--------------
    pgsql/doc/src/sgml:
        func.sgml (r1.434 -> r1.435)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.434&r2=1.435)
    pgsql/src/backend/postmaster:
        postmaster.c (r1.556 -> r1.557)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c?r1=1.556&r2=1.557)
    pgsql/src/backend/utils/adt:
        timestamp.c (r1.187 -> r1.188)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/timestamp.c?r1=1.187&r2=1.188)
    pgsql/src/backend/utils/misc:
        guc-file.l (r1.53 -> r1.54)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc-file.l?r1=1.53&r2=1.54)
    pgsql/src/include/catalog:
        catversion.h (r1.453 -> r1.454)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.453&r2=1.454)
        pg_proc.h (r1.494 -> r1.495)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.494&r2=1.495)
    pgsql/src/include/utils:
        timestamp.h (r1.76 -> r1.77)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/timestamp.h?r1=1.76&r2=1.77)