- Be clear about the safe 'memset/memcpy' operations on virtual classes.

Since I remember that 'memset/memcpy' is safe in this code, it should be okay to cast to the generic pointer all the 'virtual class' arguments before calling the above functions. Shuts up Clang warnings.
- Be more compatible with C++11 narrowing conversions system.
- reorganization of automap color handling for easier maintenance

Mostly preparation to implement a per-mod automap option but also fixes a few minor issues with some colors that are not defined in the original game specific colorsets.
- ovthingcolors were not properly set.
- added all the missing color CVARs for the overlays which previously duplicated use of one of the other CVARs.
- Ignored dehacked.exe from *.zip files to enable loading of *.deh files.
- implemented automap color parser for MAPINFO (code not tested yet!)
- fixed typo in MENUDEFS.
Merge branch 'automap_colors'
Merge branch 'master' of https://github.com/rheit/zdoom