WIP: eagle: new package

FIXME: it doesn't run! I think I've patched all there is but it errors
out when starting:

  $ ./result/eagle-6.4.0/bin/eagle
  argv[0] (/home/bfo/nixpkgs/result/eagle-6.4.0/bin/eagle) is not the currently executed program version!

  And then it's dead (exit value 4).
--

Eagle is a schematic capture and PCB layout program from CadSoft. This
is proprietary software and CadSoft provide a self-extracting shell
script with embedded tarball of the prebuilt application.

Add Eagle version 6.4.0.