allow yield* as a unary operator (fixes #372)
allow yield* as a unary operator (fixes #372)

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