* m4/m4.m4 (AC_PROG_GNU_M4): Reject m4 1.4.5, now that we use
regexp it can't handle.
* NEWS: Mention minimum version bump.
* README: Likewise.
* README-hacking: Likewise.
* doc/autoconf.texi (Introduction, Why GNU M4): Likewise.
* tests/tools.at (autom4te --trace and whitespace): Update test so
still work with older m4 line numbers.
* tests/m4sugar.at (m4@&t@_require: nested): Likewise.
Reported by Ralf Wildenhues.
Signed-off-by: Eric Blake <ebb9@byu.net>