A PortGroup for building more 32/64-bit universal packages

[Marcus Calhoun-Lopez]

I have a need of more 32/64-bit universal packages.
To facilitate this, I would like to propose a PortGroup with a different
universal build mechanism than the default.
See http://trac.macports.org/ticket/17972.

It is intended to be an improvement of the merge function.

Any feedback would be greatly appreciated.
The only time I write in Tcl is on MacPorts related projects.

-Marcus