[hack] Add Option.if_none to Common
[hack] Add Option.if_none to Common

Summary: This allows us to chain multiple matches on options, even if some match on the None case.

Reviewed By: vassilmladenov

Differential Revision: D16548323

fbshipit-source-id: 77b7be44fedf75e8715d8c5b78dd5c96dca31b5b

mroch/flow,facebook/flow,samwgoldman/flow,samwgoldman/flow,gabelevi/flow,facebook/flow,facebook/flow,gabelevi/flow,gabelevi/flow,samwgoldman/flow,facebook/flow,mroch/flow,facebook/flow,mroch/flow,samwgoldman/flow,mroch/flow,samwgoldman/flow,mroch/flow,gabelevi/flow,mroch/flow,samwgoldman/flow,mroch/flow,facebook/flow,gabelevi/flow,samwgoldman/flow,gabelevi/flow,gabelevi/flow,facebook/flow