gdb
* configure: Rebuild.
* configure.ac (READLINE_TEXI_INCFLAG): New subst.
gdb/doc
* gdb.texinfo (Top): Check SYSTEM_READLINE.
(Editing): Likewise.
(Command History): Likewise.
(TUI Keys): Likewise.
(Bug Reporting): Conditionally include rluser.texi and
inc-history.texinfo.
* Makefile.in (READLINE_TEXI_INCFLAG): New variable.
(GDB_DOC_SOURCE_INCLUDES): Add comment.
(GDBvn.texi): Set SYSTEM_READLINE when appropriate.
(gdb.dvi): Use READLINE_TEXI_INCFLAG.
(gdb.pdf): Likewise.
(gdb.info): Likewise.
(gdb/index.html): Likewise.