Don't use a sub-`configure' for `guile-readline'.

Don't use a sub-`configure' for `guile-readline'.

* acinclude.m4 (GUILE_READLINE): New macro, based on the former
  `guile-readline/configure.ac'.

* configure.ac: Remove `AC_CONFIG_SUBDIRS' invocation.  Add
  `GUILE_READLINE' invocation.  Produce files under `guile-readline'.

* guile-readline/Makefile.am: Conditionalize the meat under
  `HAVE_READLINE'.
  (INCLUDES): Rename to...
  (AM_CPPFLAGS): this.  Users updates.
  (AM_CFLAGS): New variable.
  (libguilereadline_v_@LIBGUILEREADLINE_MAJOR@_la_LIBADD): Add
  $(READLINE_LIBS).

* guile-readline/readline.c: Include <config.h>.

* guile-readline/configure.ac, guile-readline/autogen.sh: Remove.