provide deprecated MakeWeak

Fix rogerwang/nw-gyp#20 rogerwang/nw-gyp#17
Fix rogerwang/nw-gyp#15 rogerwang/nw-gyp#12
Fix rogerwang/node-webkit#533 rogerwang/node-webkit#1355
Helpful for rogerwang/node-webkit#1332
Merge branch 'nwebkit' of https://github.com/rogerwang/v8 into nwebkit