Log Message:
automake: update to 1.16.3.

New in 1.16.3:

* New features added

  - In the testsuite summary, the "for $(PACKAGE_STRING)" suffix
    can be overridden with the AM_TESTSUITE_SUMMARY_HEADER variable.

* Bugs fixed

  - Python 3.10 version number no longer considered to be 3.1.

  - Broken links in manual fixed or removed, and new script
    contrib/checklinkx (a small modification of W3C checklink) added,
    with accompany target checklinkx to recheck urls.

  - install-exec target depends on $(BUILT_SOURCES).

  - valac argument matching more precise, to avoid garbage in DIST_COMMON.

  - Support for Vala in VPATH builds fixed so that both freshly-generated and
    distributed C files work, and operation is more reliable with or without
    an installed valac.

  - Dejagnu doesn't break on directories containing spaces.

* Distribution

  - new variable AM_DISTCHECK_DVI_TARGET, to allow overriding the
    "make dvi" that is done as part of distcheck.

* Miscellaneous changes

  - install-sh tweaks:
    . new option -p to preserve mtime, i.e., invoke cp -p.
    . new option -S SUFFIX to attempt backup files using SUFFIX.
    . no longer unconditionally uses -f when rm is overridden by RMPROG.
    . does not chown existing directories.

  - Removed function up_to_date_p in lib/Automake/FileUtils.pm.
    We believe this function is completely unused.

  - Support for in-tree Vala libraries improved.