Remove use of generic lambdas
Remove use of generic lambdas

Summary:
The use of generic lambdas caused compiler errors with gcc 4.8.2.
Fixes https://github.com/facebook/folly/issues/569.

Reviewed By: Orvid, yfeldblum

Differential Revision: D4821115

fbshipit-source-id: 8372ee7695a3d0a1df0d033623618a923c261737

rklabs/folly,Orvid/folly,Orvid/folly,rklabs/folly,Orvid/folly,Orvid/folly,facebook/folly,Orvid/folly,facebook/folly,facebook/folly,rklabs/folly,rklabs/folly,rklabs/folly,facebook/folly,facebook/folly