Make Array.prototype.pop throw if the last element is not configurable.
Popping an element from an array should call [[Delete]] internal method
and pass true as the second argument (ECMA-262/5.1/#sec-15.4.4.6).
When the last element can't be deleted, throw a Type Error.
Not throwing the error would result in endless loop in the following test.

TEST=var a=[];Object.defineProperty(a,0,{});while(a.length)a.pop();

By the way fix another bug, or else i can't post any issues.
"presubmit.py" throw a "missing a correct copyright header" on windows.
Both the slash and the backslash are valid path separator on windows.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/29513004

Patch from Yanagi <admin@web-tinker.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17346 ce2b1a6d-e550-0410-aec6-3dcde31c8c00