pgsql: Hack around the discrepancy between default library search paths

Log Message:
-----------
Hack around the discrepancy between default library search paths for
gcc and for HP's ld on HPUX. There may be better ways to do this,
but this seems to work for me...

Modified Files:
--------------
pgsql/src:
Makefile.shlib (r1.92 -> r1.93)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/Makefile.shlib.diff?r1=1.92&r2=1.93)