Add UNSAFE comment for mapconstruct hack
Add UNSAFE comment for mapconstruct hack

Summary:
This will supress errors in struct constructors until we do proper cast
checking for non-basic typed fields (containers and structs).

Test Plan: Thrift still compiles

Reviewed By: jwatzman@fb.com

Subscribers: alandau, mshneer

FB internal diff: D1636028

HankFaan/fbthrift,kangkot/fbthrift,getyourguide/fbthrift,project-zerus/fbthrift,project-zerus/fbthrift,soumith/fbthrift,soumith/fbthrift,uber/fbthrift,project-zerus/fbthrift,LinusU/fbthrift,kangkot/fbthrift,SergeyMakarenko/fbthrift,Orvid/fbthrift,sinjar666/fbthrift,fengshao0907/fbthrift,sinjar666/fbthrift,jesboat/fbthrift,SergeyMakarenko/fbthrift,Orvid/fbthrift,raphaelamorim/fbthrift,Orvid/fbthrift,guker/fbthrift,guker/fbthrift,project-zerus/fbthrift,SergeyMakarenko/fbthrift,uber/fbthrift,maxwell-demon/fbthrift,chjp2046/fbthrift,fengshao0907/fbthrift,fengshao0907/fbthrift,HankFaan/fbthrift,chjp2046/fbthrift,facebook/fbthrift,soumith/fbthrift,uber/fbthrift,guker/fbthrift,project-zerus/fbthrift,maxwell-demon/fbthrift,uber/fbthrift,HankFaan/fbthrift,SergeyMakarenko/fbthrift,fengshao0907/fbthrift,chjp2046/fbthrift,Orvid/fbthrift,project-zerus/fbthrift,guker/fbthrift,kangkot/fbthrift,uber/fbthrift,maxwell-demon/fbthrift,SergeyMakarenko/fbthrift,HankFaan/fbthrift,guker/fbthrift,maxwell-demon/fbthrift,sinjar666/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,guker/fbthrift,uber/fbthrift,getyourguide/fbthrift,soumith/fbthrift,sinjar666/fbthrift,maxwell-demon/fbthrift,fengshao0907/fbthrift,soumith/fbthrift,project-zerus/fbthrift,getyourguide/fbthrift,guker/fbthrift,uber/fbthrift,SergeyMakarenko/fbthrift,HankFaan/fbthrift,uber/fbthrift,getyourguide/fbthrift,chjp2046/fbthrift,project-zerus/fbthrift,kangkot/fbthrift,getyourguide/fbthrift,Orvid/fbthrift,raphaelamorim/fbthrift,facebook/fbthrift,LinusU/fbthrift,kangkot/fbthrift,Orvid/fbthrift,jesboat/fbthrift,kangkot/fbthrift,raphaelamorim/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,raphaelamorim/fbthrift,sinjar666/fbthrift,jesboat/fbthrift,getyourguide/fbthrift,sinjar666/fbthrift,uber/fbthrift,soumith/fbthrift,LinusU/fbthrift,jesboat/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,fengshao0907/fbthrift,raphaelamorim/fbthrift,fengshao0907/fbthrift,chjp2046/fbthrift,maxwell-demon/fbthrift,HankFaan/fbthrift,getyourguide/fbthrift,guker/fbthrift,facebook/fbthrift,soumith/fbthrift,project-zerus/fbthrift,HankFaan/fbthrift,jesboat/fbthrift,kangkot/fbthrift,LinusU/fbthrift,sinjar666/fbthrift,sinjar666/fbthrift,LinusU/fbthrift,facebook/fbthrift,facebook/fbthrift,chjp2046/fbthrift,chjp2046/fbthrift,LinusU/fbthrift,fengshao0907/fbthrift,SergeyMakarenko/fbthrift,maxwell-demon/fbthrift,fengshao0907/fbthrift,maxwell-demon/fbthrift,uber/fbthrift,chjp2046/fbthrift,fengshao0907/fbthrift,jesboat/fbthrift,HankFaan/fbthrift,sinjar666/fbthrift,fengshao0907/fbthrift,raphaelamorim/fbthrift,chjp2046/fbthrift,project-zerus/fbthrift,getyourguide/fbthrift,kangkot/fbthrift,soumith/fbthrift,chjp2046/fbthrift,jesboat/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,uber/fbthrift,soumith/fbthrift,raphaelamorim/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,raphaelamorim/fbthrift,LinusU/fbthrift,facebook/fbthrift,getyourguide/fbthrift,raphaelamorim/fbthrift,LinusU/fbthrift,chjp2046/fbthrift,maxwell-demon/fbthrift,getyourguide/fbthrift,Orvid/fbthrift,raphaelamorim/fbthrift,HankFaan/fbthrift,guker/fbthrift,jesboat/fbthrift,HankFaan/fbthrift,chjp2046/fbthrift,sinjar666/fbthrift,maxwell-demon/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,uber/fbthrift,sinjar666/fbthrift,Orvid/fbthrift,soumith/fbthrift,kangkot/fbthrift,project-zerus/fbthrift,LinusU/fbthrift,guker/fbthrift,raphaelamorim/fbthrift,guker/fbthrift,Orvid/fbthrift,Orvid/fbthrift,kangkot/fbthrift,jesboat/fbthrift,Orvid/fbthrift,jesboat/fbthrift,soumith/fbthrift,jesboat/fbthrift,kangkot/fbthrift,HankFaan/fbthrift,maxwell-demon/fbthrift,project-zerus/fbthrift,jesboat/fbthrift