Fix errors reported by UBSan

[rfomin]

There are only "left shift of negative value" errors left, which may not be worth fixing.

[Pedro-Beirao]

Looks good thanks!

Its weird that it complains about P_ReplaceMobjWithIndex, but whatever.

[rfomin]

Its weird that it complains about P_ReplaceMobjWithIndex, but whatever.

The actual problem is the P_SAVE_TYPE_REF macro. One way to fix the alignment issue is to use an additional memcpy, but then the saving code will be slower.

Kraflab removed the padding in the old Doom code. See: https://github.com/coelckers/prboom-plus/blob/969515162c5aebea4ad7a125ee178dcad3d576ad/prboom2/src/p_saveg.c#L53
It seems that we can resolve the issue by restoring and updating it.

How important is misalignment? I remember at least one crash related to this issue in Woof on Linux. There are a lot of changes in this PR, so more testing is needed.