(CFLAGS): Do not include the WARNING_CFLAGS here, since GNU
Gettext doesn't compile cleanly, and dies with -Werror.
* src/Makefile.am, lib/Makefile.am, tests/atlocal.in (CFLAGS):
Include WARNING_CFLAGS here.
* lib/xstrdup.c: Include xalloc.h, so that xstrdup be declared
before being defined.
* 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.
