Add a formula for Python 3 (specifically 3.1.2).

Based off of the Python 2.6.5 formula. Minor comment tweaks along with adding
an extra performance flag that works under both gcc and LLVM.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/python3.rb

@@ -0,0 +1,44 @@
+# Lightly modified from the Python 2.6.5 formula.
+require 'formula'
+
+class Python3 <Formula
+  url 'http://www.python.org/ftp/python/3.1.2/Python-3.1.2.tar.bz2'
+  homepage 'http://www.python.org/'
+  md5 '45350b51b58a46b029fb06c61257e350'
+
+  depends_on 'readline' => :optional  # Prefer over OS X's libedit.
+  depends_on 'sqlite' => :optional  # Prefer over OS X's copy.
+  depends_on 'gdbm' => :optional
+  # With all dependencies installed should only have ossaudiodev and spwd not
+  # built from the stdlib.
+
+  def options
+    [
+      ["--framework", "Do a 'Framework' build instead of a UNIX-style build."],
+      ["--universal", "Build for both 32 & 64 bit Intel."]
+    ]
+  end
+
+  # XXX Overriding skip_clean? is deprecated
+  def skip_clean? path
+    # Need to keep the versioned binaries.
+    # Also, don't strip out pre-compiled # bytecode files.
+    path == bin+'python3' or path == bin+'python3.1' or
+    path == lib+'python3.1'
+  end
+
+  def install
+    # --with-computed-gotos requires addressable labels in C;
+    # both gcc and LLVM support this, so switch it on.
+    args = ["--prefix=#{prefix}", "--with-computed-gotos"]
+
+    args << "--enable-framework" if ARGV.include? '--framework'
+    if ARGV.include? '--universal'
+      args.push "--enable-universalsdk=/", "--with-universal-archs=intel"
+    end
+
+    system "./configure", *args
+    system "make"
+    system "make install"
+  end
+end