cdrtools and dvdrtools conflict with each other

These two packages are incompatible forks of each other with the same
binary names.

Formula/cdrtools.rb

@@ -7,6 +7,9 @@ class Cdrtools < Formula
 
   depends_on 'smake' => :build
 
+  conflicts_with 'dvdrtools',
+    :because => 'both dvdrtools and cdrtools install binaries by the same name'
+
   def install
     system "smake", "INS_BASE=#{prefix}", "INS_RBASE=#{prefix}", "install"
     # cdrtools tries to install some generic smake headers, libraries and

Formula/dvdrtools.rb

@@ -5,6 +5,9 @@ class Dvdrtools < Formula
   url 'http://savannah.nongnu.org/download/dvdrtools/dvdrtools-0.2.1.tar.gz'
   sha1 'b8b889f73953c121acd85ce1b4ba988ef7ef6bfc'
 
+  conflicts_with 'cdrtools',
+    :because => 'both cdrtools and dvdrtools install binaries by the same name'
+
   def patches
   { :p0 => [
       "https://trac.macports.org/export/89262/trunk/dports/sysutils/dvdrtools/files/patch-cdda2wav-cdda2wav.c",