Additional Button prompts for additional Controller Types (Steam Controller, Xbox 360, DualShock 3)

[AL2009man]

Looking at ButtonGlyphs.cpp and it's Button Icons: I'm surprised that certain icons for specific/shared Controller Types are omitted from the collection, given some of the controller buttons used to be the standard or the de-facto default (Select/Back and Start for Xbox 360 and PlayStation 3-and below, respectively).

Right now: the remaining button prompt missing from the pack, based on Controller Type:

• Steam Controller (Left Trackpad D-PADs, Back and Start)
• Xbox 360 (Back and Start)
• DualShock 3 (Select and Start)

looking at the current button prompt files: I suspect this Feature Request/Enhancement might require making new artwork for it; but for the sake of completion-ness (and help prepare for SDL Action Set and maybe ControllerImage), it would be nice to see the missing button prompts being added to the collection.

also: some people who still use a Xbox 360 Controller will be happy that the "Pause" button icon is a Start button instead of a "Menu" button. :P

[Daaaav]

We did originally have icons for stuff like START and SELECT, but in the end, due to the space limitations, we decided it was easier to just do those buttons with raw text instead.