Fixes a struct stat size mismatch on 64 bits machines that made Node crash with
a EXC_BAD_ACCESS on startup.
Fixes #2061 for gyp builds. Solution proposed by Paddy Byers.
Hoist common settings into common.gypi.
Restrict v8's common.gypi to v8 projects.
Ensure v8 doesn't use /MP in debug builds.
Add basic settings for other platforms.
Make uv import common.gypi properly.
Remove LTCG warning.