Topic/default/prefer type over which
Gentoo will remove which(1) from the @system set. See https://bugs.gentoo.org/646588 for background. XEmacs bug: https://bugs.gentoo.org/940218
The MR consist of tow commits. First just add the change to configure.ac. The second adds the resulting configure after running Gentoo patched autoconf 2.71 which produces more well formatted code.