The ENUM_INDEX utility was added to return the index of an enum
consistently between Dart and TypeScript, so that the index
could be used to look up the name of the enum. Since dart is no
longer supported by Http, and since no other part of the framework
is using this function, it has been removed.
Closes#3843
BREAKING CHANGE:
This change moves the http module into angular2/, so its import
path is now angular2/http instead of http/http.
Many other modules have also been moved around inside of angular2,
but the public API paths have not changed as of this commit.
