b4f9012464
A character in a fixed-form source line (as opposed to a comment or compiler directive) can't have a non-digit in its label field, columns 1 through 5. The prescanner presently emits only a warning for this case. Retain the warning for -E output, but otherwise diagnose an error. (This change affected a number of tests that relied on this situation being a warning just so that they could test prescanner warnings, and those tests were adjusted to use another warning.) Fixes https://github.com/llvm/llvm-project/issues/50563.