New formula for GiNaC

GiNaC is Not a CAS is a C++ library that supports symbolic computation
and may be used as the foundation of a Computer Algebra System (CAS).

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

Formula/ginac.rb

@@ -0,0 +1,15 @@
+require 'formula'
+
+class Ginac <Formula
+  url 'http://www.ginac.de/ginac-1.5.7.tar.bz2'
+  homepage 'http://www.ginac.de/'
+  md5 '6714dc642dec79fed35b9ba7b7a83b0a'
+
+  depends_on 'cln'
+  depends_on 'readline'
+
+  def install
+    system "./configure", "--prefix=#{prefix}", "--disable-dependency-tracking"
+    system "make install"
+  end
+end