Make it clear that WAF is preferred and rename autogen.sh

INSTALL

@@ -16,13 +16,14 @@ You can install it with './waf install'
 
 For further options run './waf --help'
 
-+++ The alternative +++
++++ Legacy support +++
 
-Alternatively, autotools build files are available.
+There are also autotools build files available. This
+is not recommended except when waf for any reason won't work.
 
-If you checked out from the repository, make sure
-you have *libtool* and *intltool* installed.
-Then run './autogen.sh'.
+Make sure you have *libtool* and *intltool* installed.
+
+Run './legacy.sh'.
 
 Run './configure'