Until now we only could inline as specialized HIR instructions when called
as a method (e.g. Math.abs)

It is very common practice to abbreviate calls to those functions by defining
a global or local variable like:

var a = Math.abs;
var x = a(123);

This change allows inlining them when called as a function (global or local).
Review URL: https://chromiumcodereview.appspot.com/9365013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10640 ce2b1a6d-e550-0410-aec6-3dcde31c8c00