Sync to latest upstream:
    
    - Generalize yield statement function type
    - Avoid crash on outrageous non-ASCII characters.
    - No longer need to pin flake8 version.
    - Find partial types anywhere in the stack. (removes local patch)
    - Update license year range to 2016
    - If a base class is Any, don't get default constructor signature from object.
    - Simplify union types when determining type sameness
    - Generator fixup
    - Add line number to "__init__ must return None" error
    - Fix empty yield error in unannotated functions
    - Fix "except (E1, E2):" parsing in PY2.
    - Don't crash if no source files were found in a directory or package.
    - Fail without traceback when duplicate module name encountered.
    - Fix subtype check between generic class and Callable
    - Avoid crash on "x in y" where y has a partial type.
    - Fix type inference issue with dict(x=[], y=[])
    - Fix #1160 (bogus error message)
    - Fix function definition within for statement