Fix silent-rules output for disabled dependency tracking.

Fix silent-rules output for disabled dependency tracking.

* lib/am/depend2.am [!%FASTDEP%]: Rework silent-rules variable
expansion code to also work in the case where %AMDEP% expands
to FALSE at config.status time, using new substitution string
%VERBOSE-NODEP%.
* automake.in (verbose_nodep_flag): New function, appending
`@am__nodep@' to the verbose-variable name.
(handle_languages): If dependencies are not disabled, use it to
set %VERBOSE-NODEP%.
* m4/depend.m4: Substitute am__nodep as '_no', so the second
verbose-variable will always expand to an empty string, if
dependencies are enabled.
* tests/silent5.test: Also test --disable-dependency-tracking;
also test per-target flags for non-C language files.
* tests/silent9.test: New test, like silent4.test but disable
dependency tracking.
* tests/Makefile.am: Adjust.
* NEWS, THANKS: Update.
Report by Dmitry V. Levin <ldv@altlinux.org>.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>