First Merge request on Qt6

[garnerm91]

In V213 SLCAN would send custom frames V220 appears to have broke that. I don't have QT5 installed so I can't help troubleshoot it.

QT6WIP is broken it current doesn't build due to issues in the class DBC_SIGNAL once that issues is fixed I got it to come up but it still has the bugs in SLCAN that cause a buffer overflow resulting in windows killing the process. As for the DBC fix I don't want to try to merge it because I haven't tested that part.

Bug fix for QT6 is to redim buffer at line 183
int sizeneed = buildStr.length() + (frame.payload().length()*2) +1; buffer.resize(sizeneed); foreach (QChar chr, buildStr) { buffer[idx] = chr.toLatin1(); idx++; }

bug fix for QT6 crashing on Save settings:
at line 125
buffer.append((char)0xF1);
I made pull request. I can do more testing on SLCAN just let me know what might not actually be tested.