Testsuite portability update round.

Testsuite portability update round.

* tests/inherited_flags: skip when shared libs are disabled.
* tests/deplibs-ident.at [ aix ]: No unexpected failure here.
* tests/libtoolize.at: Fix for distcheck (readonly sources).
* tests/nonrecursive.at, tests/recursive.at, tests/subproject.at
(foo.c): Actually export a symbol, for AIX.
* tests/old-m4-iface.at: Use AC_LIBTOOL_DLOPEN, for AIX.
* tests/nonrecursive.at: Set foo_la_SOURCES, for automake-1.7.
* tests/subproject.at: Require automake-1.9, we use indirect
subdirs.
* tests/am-subdir.at: Move AT_KEYWORDS settings..
* tests/testsuite.at: ..here, in respective macros.
(LT_AT_AUTOMAKE): Skip if we detect failure due to old version.
(PREPARE_TESTS): Set autotool variables to `no' if not present.
(LT_AT_ACLOCAL, LT_AT_AUTOCONF, LT_AT_AUTOMAKE)
(LT_AT_AUTOHEADER, LT_AT_AUTORECONF): Use to XFAIL tests.
Reported by Tim Rice <tim@multitalents.net>.
(LT_AT_MAKE): Do not use `make -e'.
(_LTDL_PROJECT_FILES): Adjust sub-make call.  Work around `make'
which does not set `MAKE' or `SHELL'.  Fix for user-set
`CONFIG_SHELL'.
Reported by Charles Wilson <cygwin@cwilson.fastmail.fm>.