syntax-check: fix violations and implement sc_prohibit_bare_basename.

syntax-check: fix violations and implement sc_prohibit_bare_basename.

* cfg.mk (sc_prohibit_bare_basename, sc_prohibit_basename_with_sed):
Make sure not to go back to using occasional `|$basename' or
`|$dirname' syntax.
* build-aux/git-hooks/commit-msg, build-aux/ltmain.m4sh,
* build-aux/options-parser, tests/fcdemo-conf.test,
* tests/fcdemo-shared.test, tests/fcdemo-static.test,
* tests/libtoolize.at: Fix violations.

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