[Ovmsdev] DBC : proposal fix for negative integer numbers having wrong values

Dear list, I've come across an issue with the DBC parser where a non-32-bit negative number was incorrectly decoded. I've traced this to an issue with sign-extension ; and I've proposed a fix here https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/pull/736 Before having it merged, I'd like to gather some feedback from users of the DBC module. Please have a look, and comment directly on the GitHub PR. Thanks in advance ! Regards, Ludovic