- added Marisa Kirisame's CHAN_OVERLAP flag.
- exported S_IsActorPlayingSomething to ZScript.
The sound API change required deprecating A_PlaySound and S_Sound. There are now new variants S_StartSound and A_StartSound which have two distinct parameters for channel and flags.
Rationale:
When a mod adds a custom option menu, it adds a space before it, like this:
```
AddOptionMenu OptionsMenu
{
StaticText ""
Submenu "$MYTITLE", MyOptions
}
```
to prevent custom option menu being in the same block as the last entries in the
standard options list. It's okay.
But when more than one such mod is loaded, each one of them adds a space before
their option menu entry, and Options Menu becomes unnecessary bloated.
This simple edit allows mods to not add a space, still be separated from
standard options.
This was yet another piece of code that essentially was unworkable thanks to the limited screen space with the old bitmap fonts.
With the new font there is enough screen space to do this properly.
