#12 link with gcc on FreeBSD, to avoid un-init structures

[Douglas Jackson]

The current configure script doesn't specifically
recognize the FreeBSD operating system.

It defaults to using the ld command directly to link the
shared library.

This causes some problems with the shared library
loader, with the result being that some commands
like "statement" are not properly recognized, and
dispatched.

A very good article at http://www.fpx.de/fp/Software/tcl-
c++/tcl-c++.html describes some of the issues with
linking loadable libraries for TCL.

Apparently this issue was known to some porters in the
past, because the Linux and windows sections in the
configure script already do this.

Doug