gnulib: fix use of link libraries.

* Makefile.am (m4_LDADD): Update link libraries accordingly.
* THANKS: Update.
Reported by Rainer Tammer.

Signed-off-by: Eric Blake <eblake@redhat.com>
maint: import release notes from branch-1.4.

* NEWS: Add entries from releases 1.4.15 thru 1.4.17.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
maint: test bad format string crash.

* doc/m4.texi (Format): Add a test.

Signed-off-by: Eric Blake <eblake@redhat.com>
m4: avoid a crash with bad format string.

* src/format.c (expand_format): Fix off-by-one error.
* THANKS: Add Carlo Teubner.

Copyright-paperwork-exempt: Yes
Signed-off-by: Eric Blake <eblake@redhat.com>
m4: avoid spurious output with unrecognized format specifiers.

* modules/format.c (format): Advance the loop invariants past an
unrecognized format specifier to avoid printing the specifier
character on the next pass.
* doc/m4.texi (Format): Don't expect unrecognized specifiers to
be output by format macro.
* tests/null.out: Don't expect unrecognized null specifier to be
output.
* tests/generate.awk (new_test): Treat `ignore' in expected error
output the same as Autotest.
* doc/m4.texi (Format): Use special `ignore' string rather than
unsupported @comment xerr magic.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
maint: clean up compiler warnings.

* modules/evalparse.c (unary_term): Likewise.
* m4/input.c (match_input): Likewise.  Also drop useless casts to
void.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
docs: mention more history

* doc/m4.texinfo (History): Add upcoming 1.4.16 release.

Signed-off-by: Eric Blake <eblake@redhat.com>
build: work around glibc and libsigsegv bugs

* docs/m4.texinfo (Index macro): Expose strstr bug.

Signed-off-by: Eric Blake <eblake@redhat.com>