etc: switch to automake

There's no content in here currently, so switching to automake is
pretty easy with a stub file.

etc/configure.ac

@@ -1,26 +1,9 @@
 dnl Process this file with autoconf to produce a configure script.
-AC_INIT(Makefile.in)
+AC_INIT([etc], [0])
 
-AC_PROG_INSTALL
+AM_MAINTAINER_MODE
+AM_INIT_AUTOMAKE
+AM_SILENT_RULES([yes])
 
-# Command-line options.
-# Very limited version of AC_MAINTAINER_MODE.
-AC_ARG_ENABLE([maintainer-mode],
-  [AC_HELP_STRING([--enable-maintainer-mode],
-                 [enable make rules and dependencies not useful (and
-                  sometimes confusing) to the casual installer])],
-  [case ${enable_maintainer_mode} in
-     yes) MAINT='' ;;
-     no) MAINT='#' ;;
-     *) AC_MSG_ERROR([--enable-maintainer-mode must be yes or no]) ;;
-   esac
-   maintainer_mode=${enableval}],
-  [MAINT='#'])
-AC_SUBST([MAINT])dnl
-
-AC_SUBST(datarootdir)
-AC_SUBST(docdir)
-AC_SUBST(htmldir)
-AC_SUBST(pdfdir)
-
-AC_OUTPUT(Makefile)
+AC_CONFIG_FILES([Makefile])
+AC_OUTPUT