Fix various shortcomings of the warnings infrastructure.

- The flags are now interpreted from left to right, without any other
precedence rule. The previous one did not make much sense in interactive
mode.
- Set Warnings and Set Warnings Append are now synonyms, and have the
"append" semantics, which is the most natural one for warnings.
- Warnings on unknown warnings are now printed only once (previously the
would be repeated on further calls to Set Warnings, sections closing,
module requiring...).
- Warning status strings are normalized, so that e.g. "+foo,-foo" is reduced
to "-foo" (if foo exists, "" otherwise).

0 files changed, 0 insertions, 0 deletions