tests: check the "%define variant" is deprecated.

tests: check the "%define variant" is deprecated.

* tests/input.at: Rename some AT_SETUP to avoid that
AT_SETUP_STRIP thinks they contain %define directives.
("%define" backward compatibility): Merge tests together
to speed up the test suite, and to make maintenance easier
(multiple AT_CHECK means multiple runs of the test suite to
be sure to have updated all the error messages).
Check the "%define variant" is properly obsoleted.