Default to little endian on windows
Default to little endian on windows

Summary:
Because MSVC doesn't provide any way for us to detect which we are actually on.
Closes https://github.com/facebook/fbthrift/pull/110

Reviewed By: juchem, yfeldblum

Differential Revision: D2853371

Pulled By: Orvid

fb-gh-sync-id: edfde892bdef573590a6c10c1728ccf7417d2c4a

getyourguide/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,facebook/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,facebook/fbthrift,facebook/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,facebook/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift