Introduce msglvl_t to unify msglevel type handling

Introduce msglvl_t to unify msglevel type handling

msglevel was definitely unsigned as the first
argument to msg(), but many parts of the code
had it as signed. So this produced a LOT of
warnings when enabling -Wsign-conversion.

Introduce a msglvl_t typedef and switch all
users to it. This includes any values that
are stored in the msglevel field, including
debug level and mute level.

There is one exception in struct status_output
where -1 is a valid value in the API. Only
positive values are translated into standard
message levels.

Change-Id: Id492cb774c6d022d06bb3cf5fec2a4bdd410e619
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1110
Message-Id: <20250917170428.3310-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg33028.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>