Problem building a new pkgsrc package

[Chris Ross <cross+netbsd%distal.com@localhost>]

  I'm trying to make a new package for pkgsrc, following the guide at
http://www.netbsd.org/docs/pkgsrc/creating.html and having a problem
based on the filename.  FYI, I'm on a NetBSD 4.0 machine, with a HEAD
pkgsrc.  I've installed url2pkg and pkglint.

  Sadly, the URL for the original source to my package is:

http://go6.net/4105/file.asp?file_id=142

  The header from that request includes:

Content-Disposition: filename=gw6c-5_0-RELEASE-src.tar.gz
Content-Type: application/x-msdownload

...and firefox is able to figure that out.  But, since url2pkg knows
nothing about that, it presumes the package name is "file", and
the extension is ".asp?file_id=142".  This *almost* works, but line 141
of pkgsrc/mk/fetch/fetch.mk has:

${DISTDIR}/${_file_}: fetch-check-interactive do-fetch-file error-check

and _file_ includes "file.asp?file_id=142".  This causes make to decide
there's a variable declaration on that line.  I haven't yet found a way
to make make(1) figure out that it's a filename, not a variable
declaration.  So, two questions:

  1) Is there a way to tell the pkgsrc system "the URL to request is
XXX, but please have the file saved into DISTDIR named YYYY instead"?
  2) Does anyone know how to have a filename that includes an '=' as
a rule target with NetBSD's make?

  Thanks...

                             - Chris