FREESCAPE: DOS/CGA render mode need work

[neuromancer]

The DOS/CGA rendering mode in Freescape games need a good amount of work to match their original implementations. A few important points:

• The palette selection is made manually using an C++ array, while it is likely to be contained in some table in the executables.
• Flashing colors are not correct, the information should be there, but it is unclear where.