syntax-check: fix violations and re-enable sc_space_tab.

syntax-check: fix violations and re-enable sc_space_tab.

* cfg.mk (local-checks-to-fix): Remove sc_space_tab from list of
disabled checks.
(exclude_file_name_regexp--sc_space_tab): Don't flag space-tab
sequences in diff files as an error.
* Makefile.am, build-aux/general.m4sh, build-aux/git-hooks/commit-msg,
build-aux/ltmain.m4sh, libltdl/loaders/dyld.c,
libltdl/loaders/shl_load.c, libltdl/ltdl.h, libltdl/ltdl.mk,
libltdl/slist.c, libtoolize.m4sh, m4/ltoptions.m4, tests/demo/dlmain.c,
tests/depdemo/main.c, tests/libtoolize.at, tests/lt_dladvise.at,
tests/pdemo/longer_file_name_dlmain.c, tests/sh.test, tests/static.at,
tests/stresstest.at, tests/template.at: Fix space-tab sequences by
reversing them in regexps, and deleting leading spaces in indentation.

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