0.9.2.4

Implemented mark specials. Demonstration: https://www.youtube.com/watch?v=MoveGeEkNmA
Implemented flood fill for boom transfer heights special.
Implemented scrolling floor/ceiling for boom transfer heights special.
Implemented iwad selector menu. Will display any iwads in the Helion directory and search common steam install paths.
Implemented loading screens.
Implemented checks for plane clipping when transitioning between transfer height sectors. Fixes rendering glitches when the plane is close to the camera Z and deals with interpolation issues when changing above/below transfer heights.
Config file command line argument (-config).
Linux will write config.ini to either $XDG_CONFIG_HOME/helion/config.ini or $HOME/.config/helion/config.ini.
Included libfluidsynth and updated NFluidsynth to load locally with linux build.
Added player options to the menu.
Triggers that transfer specials will now transfer/clear secret flag.
Fixed dropped flag not being carried over when applying dehacked flags that caused double the ammo to be picked up.
Updated TNT1 state to use Actor::spawn. Fixes Machete MAP10 exit.
Fixed infinite weapon cycling error that occurred when attempting to cycle weapons when in chasecam.
Fixed missing SAWB2 mapping for dehacked.
Fixed saving empty keys to the configuration so that the key binding isn't reset to the pre-defined defaults.
Key binding checks for mouse wheel scrolling.
Fixed scroll texture model specials. Fixes boom specials 218 and 249.
Fixed light banding offset calculation in shader to account for when zNear is modified.
Fixed transfer specials that change flat from or to a sky texture.
Fixed upper/lower flood calculations for when the flat texture is a sky.