Remove mz-scheme

mz-scheme does not build on Lion, and has been superceded by Racket.
We would accept pull requests for mz-scheme in Homebrew-Alt if
access to this older version is still desired.

Formula/mz-scheme.rb

@@ -1,23 +0,0 @@
-require 'formula'
-
-class MzScheme < Formula
-  url 'http://download.plt-scheme.org/bundles/4.2.5/mz/mz-4.2.5-src-unix.tgz'
-  homepage 'http://plt-scheme.org/'
-  md5 '5d320c94e168ab58237c0e710c6050d0'
-  version '4.2.5'
-
-  fails_with_llvm "Unsupported inline asm", :build => 2335
-
-  def install
-    cd "src"
-
-    args = ["--disable-debug", "--disable-dependency-tracking",
-            "--disable-pthread", "--disable-mred", "--enable-xonx",
-            "--prefix=#{prefix}"]
-    args << "--enable-mac64" if MacOS.prefer_64_bit?
-
-    system "./configure", *args
-    system "make"
-    system "make install"
-  end
-end