Mod-specific frontend level support

[TheEnbyWitch]

This simply allows game_mod to load a mod_frontend level instead of the regular one if one exists. The only thing that doesn't work is when you quit a level, BO1 can't find the mod_frontend level.

Demonstration: https://www.youtube.com/watch?v=ojtoC5IeJe0

[Arefu]

@SE2Dev Decline this PR Kappa

[TheEnbyWitch]

Why kappa

[iAmThatMichael]

wouldn't there be more cases for frontend to load such as through menu's?

[SE2Dev]

@DidUknowiPwn yes - and a proper fallback handler would be needed.

[Arefu]

@Ray1235 😏

[TheEnbyWitch]

The only case where it didn't work was when exiting the game. It couldn't find the d3dbsp for the mod_frontend level

[SE2Dev]

Try devmap frontend etc.