https://github.com/EpicGames/UnrealEngine/pull/651
During a recent project, we needed to patch in support for input plugins on iOS and Mac and we decided to share that work with the community via this pull request.
Kudos and gratitude to our friends at Big Blue Studios - Mircea Cenghia & Cristian Tudor - for their help. 
Note that getting the plugins to work takes no additional effort outside a normal workflow, so no instructions are needed really.
Enjoy!