bootstrap: sync with upstream.

* gl/build-aux/bootstrap.in, gl/build-aux/extract-trace,
gl/build-aux/funclib.sh, gl/build-aux/options-parser: Update from
upstream to pick up recent improvements.
* bootstrap: Regenerate.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
maint: add missing ChangeLog entry.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
bootstrap: don't double-specify --no-changelog to gnulib-tool.

* bootstrap.conf (gnulib_tool_option_extras): Rename from this...
(gnulib_tool_options): ...this, and append options rather than
overwrite.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
bootstrap: require newer texinfo release.

* bootstrap.conf (buildreq): Bump required makeinfo binary
release number to 4.13 to support --build-dir option.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
configury: specify subdir-objects for future automake releases.

Latest automake warns about future incompatibility if subdir-objects
is not specified by AM_INIT_AUTOMAKE.
* configure.ac (AM_INIT_AUTOMAKE): Add subdir-objects.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>