* tests/calc.at (_AT_CHECK_CALC_ERROR): Receive as argument the

* tests/calc.at (_AT_CHECK_CALC_ERROR): Receive as argument the
full stderr, and strip it according to the bison options, instead
of composing the error message from different bits.
This makes it easier to check for several error messages.
Adjust all the invocations.
Add an invocation exercising the error token.
Add an invocation demonstrating a stupid error message.
(_AT_DATA_CALC_Y): Follow the GCS: initial column is 1, not 0.
Adjust the tests.
Error message are for stderr, not stdout.