pgsql: I find that an out-of-the-box installation of OSSP uuid 1.6.0

Log Message:
-----------
I find that an out-of-the-box installation of OSSP uuid 1.6.0 installs
itself as libuuid, not libossp-uuid which was the only case expected by
our build support.  Install a configure test to determine which name
to use (and to check that the library is present at all).

Modified Files:
--------------
    pgsql:
        configure.in (r1.535 -> r1.536)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.in?r1=1.535&r2=1.536)
        configure (r1.569 -> r1.570)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure?r1=1.569&r2=1.570)
    pgsql/src:
        Makefile.global.in (r1.239 -> r1.240)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/Makefile.global.in?r1=1.239&r2=1.240)
    pgsql/contrib/uuid-ossp:
        Makefile (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/uuid-ossp/Makefile?r1=1.3&r2=1.4)