pgsql: Closer code review for PQconnectionUsedPassword() patch: in

Log Message:
-----------
Closer code review for PQconnectionUsedPassword() patch: in particular,
not OK to include postgres_fe.h into libpq-fe.h, hence declare it as
returning int not bool.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        libpq.sgml (r1.236 -> r1.237)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/libpq.sgml.diff?r1=1.236&r2=1.237)
    pgsql/src/include/libpq:
        pqcomm.h (r1.103 -> r1.104)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/libpq/pqcomm.h.diff?r1=1.103&r2=1.104)
    pgsql/src/interfaces/libpq:
        fe-connect.c (r1.346 -> r1.347)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-connect.c.diff?r1=1.346&r2=1.347)
        libpq-fe.h (r1.137 -> r1.138)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-fe.h.diff?r1=1.137&r2=1.138)
        libpq-int.h (r1.120 -> r1.121)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-int.h.diff?r1=1.120&r2=1.121)