config.status: consistent exit status with nonexistent config file input.

config.status: consistent exit status with nonexistent config file input.

* lib/autoconf/status.m4 (_AC_OUTPUT_MAIN_LOOP): Ensure we
exit with status 1 rather than with that of 'false', for
reproducibility.
(AC_OUTPUT): Ensure to exit 1 in case of config.status failure.
* tests/torture.at (Missing templates): Also test code path
for $srcdir != '.'.
Report by Tim Rice.