nwsnapshot support

Conflicts:
	include/v8.h
	src/api.cc
	src/compiler.cc
	src/compiler.h
	src/mksnapshot.cc
	src/objects.h
	src/snapshot-common.cc
	src/snapshot.h
	tools/gyp/v8.gyp
add missing nwsnapshot.cc
Fix nwsnapshot for nw11

Fix rogerwang/node-webkit#2594