Revise installation instructions and add what you need to do if you want to develop libcdio

README.develop

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+Software you'll need to build a development version libcdio
+  - git
+  - autoconf (which contains programs autoconf and autoreconf)
+  - automake 
+  - m4 (used by autoconf)
+  - texinfo (for building documentation)
+
+This is in addition to the software needed to build starting from a the 
+source tar. See README.libcdio for that additional software.
+
+The source code lives the GNU software repository https://savannah.gnu.org/
+The main page Savannah page is 
+  https://savannah.gnu.org/projects/libcdio/
+
+If you check out the source code, you'll need git installed. See the git
+tab of the libcdio project https://savannah.gnu.org/git/?group=libcdio
+which has an additional link for how to get "git".
+
+One you have git:
+
+   git clone git://git.savannah.gnu.org/libcdio.git   
+
+Change into the libcdio directory that just created and run the "autogen.sh"
+shell script
+
+  cd libcdio
+  sh ./autogen.sh 
+
+Please see README.libcdio and follow those instructions starting at step 3.
+Normally autogen doesn't