carry over entire builtin macro environment #127
carry over entire builtin macro environment #127

All compile-time values defined in the `builtinSource` need to be
carried over to the main expasion. This allows exported macros to
safely generate non-exported macros.

dashersw/sweet.js,mozilla/sweet.js,renyaoxiang/sweet.js,sweet-js/sweet-core,getshuvo/sweet.js,lukehoban/sweet.js,dashersw/sweet.js,renyaoxiang/sweet.js,sweet-js/sweet.js,mozilla/sweet.js,lukehoban/sweet.js,getshuvo/sweet.js,sweet-js/sweet.js