pgsql: Use -fPIC not -fpic for BSDen on Sparc.

Log Message:
-----------
Use -fPIC not -fpic for BSDen on Sparc.  Also switch from
$(LD) -x -Bshareable to $(CC) -shared on OpenBSD (I suspect this
should be carried over to the other two as well, but will refrain
pending suggestions from people who actually use those platforms).
Per Stefan Kaltenbrunner.

Modified Files:
--------------
    pgsql/src/makefiles:
        Makefile.freebsd (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/makefiles/Makefile.freebsd.diff?r1=1.16&r2=1.17)
        Makefile.netbsd (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/makefiles/Makefile.netbsd.diff?r1=1.8&r2=1.9)
        Makefile.openbsd (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/makefiles/Makefile.openbsd.diff?r1=1.8&r2=1.9)