Revert "remote old generator stuff"

This reverts commit b3dde7b445dfd5f2d83a898677dffc9260927093.
define adapter object for es6-style generator emulator
declare IteratorResult as a fake class
implement generator emulation helpers in bootstrap.js
follow API change of __jsx_generator_object
StopIteration no longer used
rename jsxGeneratorObject
add missing close parentheses
fix small bugs introduced in copipe
add a compiler flag: --enable-generator-emulation
get rid of wrong 'new'
add a todo test
enable generator expressions
for-in is still todo