[clang frontend] Make DeclStmt return empty exps
[clang frontend] Make DeclStmt return empty exps

Summary:
Stmt shouldn't have to return anything in res_trans.exps - those results shouldn't be used by parent nodes.
I need this change for another diff but given the risk I decided to put it as separate diff

Reviewed By: jvillard

Differential Revision: D4474936

fbshipit-source-id: 0537749

jvillard/infer,jsachs/infer,ropas/infer,jsachs/infer,ryoon/infer,blzq/infer,ropas/infer,jsachs/infer,facebook/infer,jsachs/infer,ryoon/infer,blzq/infer,ryoon/infer,ropas/infer,ryoon/infer,ropas/infer,facebook/infer,jvillard/infer,facebook/infer,facebook/infer,ropas/infer,jvillard/infer,jvillard/infer,blzq/infer,blzq/infer,facebook/infer,facebook/infer,jsachs/infer,jvillard/infer,jvillard/infer,facebook/infer,jvillard/infer,ryoon/infer,blzq/infer,ryoon/infer,ropas/infer,blzq/infer,jsachs/infer