Pack PackedSyncPtr
Pack PackedSyncPtr

Summary: The comment was right about the packed attribute not liking private members, so pack `PackedSyncPtr` to get GCC to pack structs containing it correctly.

Reviewed By: yfeldblum

Differential Revision: D3402936

fbshipit-source-id: 11d9def132d5dedf04b0e263c379cac339a52fa3

Orvid/folly,rklabs/folly,brunomorishita/folly,mqeizi/folly,rklabs/folly,mqeizi/folly,charsyam/folly,floxard/folly,rklabs/folly,facebook/folly,charsyam/folly,mqeizi/folly,rklabs/folly,floxard/folly,floxard/folly,Orvid/folly,facebook/folly,mqeizi/folly,brunomorishita/folly,mqeizi/folly,facebook/folly,Orvid/folly,Orvid/folly,charsyam/folly,floxard/folly,brunomorishita/folly,rklabs/folly,facebook/folly,charsyam/folly,floxard/folly,Orvid/folly,brunomorishita/folly,facebook/folly,brunomorishita/folly