Basic support for "#else" preprocessor in AGS script

[ivan-mogilko]

I could not find if there was there a ticket for this, maybe I had a false memory about it.

In any case, I got weary of not being able to have #ifdef N #else #endif kind of construct, and tried to implement basic support for "#else".

This is a most trivial and naive implementation, because it assumes only ifdef/else/endif combination. This won't work with "else if", but these are not supported by AGS preprocessor at the moment.

Added to:

• Editor's preprocessor (C# one);
• Editor's Autocomplete. Although autocomplete seems to break often when preprocessor definitions are around, but that might be a separate issue. At least it seems to work when the #if/else/endif are on top of the script (outside of function).
• C++ preprocessor, to sync with the embedded C# one.

If this proves to be working, and merged, then we could also tidy builtin header where declarations depend on SCRIPT_API macros.

PS. I still think we should get a proper complete preprocessor into AGS from somewhere else at some point.

[ericoporto]

It would be nice to add a demonstrative test case in https://github.com/adventuregamestudio/ags/blob/master/Compiler/test/preprocessor_test.cpp

[ericoporto]

Looks good to merge! :)