tests: migrate tests/sh.test checks to syntax-checks.

tests: migrate tests/sh.test checks to syntax-checks.

Some modernization of the legacy testsuite.
* tests/sh.test: Remove.
* Makefile.am (COMMON_TESTS): Adjust.
* cfg.mk (sc_libtool_m4_cc_basename, sc_prohibit_bracket_as_test)
(sc_prohibit_nested_quotes, sc_prohibit_set_dummy_without_shift)
(sc_prohibit_set_minus_minus, sc_prohibit_test_binary_operators)
(sc_prohibit_test_dollar, sc_prohibit_test_minus_e)
(sc_prohibit_test_unary_operators, sc_prohibit_test_X)
(sc_prohibit_Xsed_withou_X, sc_require_function_nl_brace):
Functionally identical tests to what used to be performed by
sh.test, only with coverage of all files.
* bootstrap, build-aux/edit-readme-alpha,
build-aux/extract-trace, build-aux/getopt.m4sh,
build-aux/ltmain.m4sh, configure.ac, m4/libtool.m4, m4/ltdl.m4,
tests/bindir.at, tests/configure-iface.at, tests/cwrapper.at,
tests/darwin.at, tests/defs.m4sh, tests/demo-hardcode.test,
tests/dlloader-api.at, tests/exceptions.at,
tests/getopt-m4sh.at, tests/lalib-syntax.at, tests/link-2.test,
tests/link-order2.at, tests/loadlibrary.at,
tests/lt_dladvise.at, tests/lt_dlexit.at, tests/lt_dlopen_a.at,
tests/lt_dlopenext.at, tests/need_lib_prefix.at,
tests/nonrecursive.at, tests/recursive.at, tests/resident.at,
tests/standalone.at, tests/static.at, tests/stresstest.at,
tests/subproject.at, tests/sysroot.at, tests/tagtrace.test,
tests/testsuite.at: Fix violations of the new syntax checks.

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