Updating apple-gcc42

[O]

Hi, I'd really like to update the apple-gcc42 port so that users can
compile kde software on OS 10.4.
The reason I want to do this are all laid out in
https://trac.macports.org/ticket/16666 so please read that before
asking why here.

In short: kde won't work without an up to date c++ compiler.
The current apple-gcc42 doesn't compile c++, even if it did, it has
bugs so it still won't work.
Bumping the rev of that port is not enough to get it to work.

Potential issues. The port attached to the ticket installs to /usr, not $prefix.