Add performance built-in to Guide
Add performance built-in to Guide

Also clarify 'global' binding removal.

svaarala/duktape,svaarala/duktape,svaarala/duktape,markand/duktape,markand/duktape,svaarala/duktape,markand/duktape,svaarala/duktape,markand/duktape,markand/duktape,svaarala/duktape,svaarala/duktape,svaarala/duktape,markand/duktape,markand/duktape,markand/duktape,svaarala/duktape,markand/duktape,markand/duktape