fix THeader.cpp double inclusion
fix THeader.cpp double inclusion

Summary:
Double inclusion was resulting in a double free of THeader::CLIENT_TIMEOUT_HEADER
which showed up in proxygen's SessionTests never completing

Test Plan: facebook/run_job.sh for proxygen and thrift

Reviewed By: davejwatson@fb.com

Subscribers: bmatheny, mshneer, viswanath, alandau, pavlo

FB internal diff: D1761157

Tasks: 5906929

Signature: t1:1761157:1420220662:bb3c39ce2488633b1b3197adb07fefa3fbb9c5eb

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