* tests/calc.at, tests/output.at, tests/regression.at,

* tests/testsuite.at, tests/torture.at: Rely on Autotest 2.52g:
now the tests are run in private dirs, therefore AC_CLEANUP and
family can be simplified to 0-ary.
* tests/atlocal.in: Now that we run `elsewhere' than in tests/,
use abs. path to find config.h.
* tests/calc.at (AT_CHECK_CALC): Don't try to check the compiler's
stderr, there can be way too much random noise.
Instead pass -Werror to GCC and rely on the exit status.
Reported by Wolfram Wagner.

tests/torture.at

@@ -73,7 +73,6 @@ main (int argc, const char **argv)
 ]])
 AT_CHECK([bison input.y -o input.c])
 AT_CHECK([$CC $CFLAGS $CPPFLAGS input.c -o input], 0, [], [ignore])
-AT_CLEANUP_FILES(input input.c)
 ])