Change function_decl to take a loc instead of a reason
Change function_decl to take a loc instead of a reason

Summary: Consolidate reasons from mk_arrow and mk_function

Reviewed By: mroch

Differential Revision: D4920920

fbshipit-source-id: 71e7782d83c8ecbe75b4a7dc63e71757e203cd35

facebook/flow,JonathanUsername/flow,mroch/flow,gabelevi/flow,jamesgpearce/flow,popham/flow,claudiopro/flow,nmote/flow,gabelevi/flow,nmote/flow,facebook/flow,TiddoLangerak/flow,AgentME/flow,MichaelDeBoey/flow,TiddoLangerak/flow,gabelevi/flow,facebook/flow,samwgoldman/flow,facebook/flow,TiddoLangerak/flow,ylu1317/flow,fletcherw/flow,JonathanUsername/flow,nmote/flow,nmote/flow,ylu1317/flow,mroch/flow,MichaelDeBoey/flow,ylu1317/flow,ylu1317/flow,MichaelDeBoey/flow,mroch/flow,mroch/flow,fletcherw/flow,mroch/flow,gabelevi/flow,nmote/flow,popham/flow,mroch/flow,AgentME/flow,jamesgpearce/flow,samwgoldman/flow,TiddoLangerak/flow,mroch/flow,ylu1317/flow,MichaelDeBoey/flow,popham/flow,samwgoldman/flow,JonathanUsername/flow,facebook/flow,popham/flow,claudiopro/flow,JonathanUsername/flow,MichaelDeBoey/flow,samwgoldman/flow,AgentME/flow,claudiopro/flow,jamesgpearce/flow,facebook/flow,JonathanUsername/flow,gabelevi/flow,samwgoldman/flow,JonathanUsername/flow,popham/flow,nmote/flow,TiddoLangerak/flow,fletcherw/flow,facebook/flow,AgentME/flow,gabelevi/flow,jamesgpearce/flow,popham/flow,samwgoldman/flow,nmote/flow,claudiopro/flow,jamesgpearce/flow,popham/flow,JonathanUsername/flow,jamesgpearce/flow,samwgoldman/flow,fletcherw/flow,fletcherw/flow,AgentME/flow,gabelevi/flow,fletcherw/flow,jamesgpearce/flow,claudiopro/flow