[Some Clients] Ultrawide support

IW4x-SP, IW4x, and IW6-Mod support ultra-wide monitors.

IW4x-SP and IW4x have the dvar r_customAspectRatio.

IW6-Mod has the dvar r_aspectRatioCustom.

The dvar can be described as follows:

Screen aspect ratio. Divide the width by the height to get the aspect ratio value. For example: 16 / 9 = 1.77

For example:

21/9 = 2.333
32/9 = 3.444

Finally, you must set the r_aspectRatio dvar to custom.