universal_variant depending on universal_archs

[Marcus Calhoun-Lopez]

Recently, the universal variant of libffi was disabled
(http://trac.macports.org/changeset/44994/trunk/dports/devel/libffi/Portfile).

After a little experimentation, it seems getting full universal to work would
be an unpleasant undertaking.
Building a 32/64 bit universal seems to work fine though:
foreach arch ${universal_archs} {
	if { ${os.arch}=="i386" && (${arch}=="ppc" || ${arch}=="ppc64") } {
		universal_variant   no
	}
        if { ${os.arch}=="powerpc" && (${arch}=="i368" || ${arch}=="x86_64") } {
		universal_variant   no
	}
}

Such a change might cause difficulties for Portindex.
Even still, might this be a reasonable solution?

-Marcus