run "strip" optimizer if --minify
autogenerated default constructor should inherit __export__ from class
do not remove native class with source if any of its static properties are used
add test covering prev. commit
add failing test
[unclassify] #toString() should not be rewritten to static function call
Merge branch 'kazuho/unclassify-vs-tostring'
Merge branch 'master' into kazuho/experiments/strip