Added gnome-common formula.

gnome-common is a module that is required only when
building GNOME from the repository.

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

Formula/gnome-common.rb

@@ -0,0 +1,12 @@
+require 'formula'
+
+class GnomeCommon <Formula
+  url 'http://ftp.gnome.org/pub/gnome/sources/gnome-common/2.28/gnome-common-2.28.0.tar.gz'
+  homepage 'http://git.gnome.org/browse/gnome-common/'
+  md5 'c85414eb4538961973f9f68fcdb96c58'
+
+  def install
+    system "./configure", "--prefix=#{prefix}"
+    system "make install"
+  end
+end