Make (some) functions called from builtin functions use the callback's global as...

Make (some) functions called from builtin functions use the callback's global as receiver.

Changes GetGlobalReceiver() to GetDefaultReceiver(func) that returns undefined
for strict and native functions, and the function's context's global proxy
for "normal" functions.

BUG=v8:1547
TEST=cctest/api-test/ForeignFunctionReceiver

Review URL: http://codereview.chromium.org/7741042

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9030 ce2b1a6d-e550-0410-aec6-3dcde31c8c00