[hack] work around ListLabels.sort_uniq being missing in ocaml 4.02
[hack] work around ListLabels.sort_uniq being missing in ocaml 4.02

Reviewed By: avikchaudhuri

Differential Revision: D4562058

fbshipit-source-id: a19f2808afcc2789dff3eb308f2e23d957f5a2ab

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