fix bytes literal creation from compile-time DEF expressions (used to become Unicode strings due to missing encoding)

This avoids the issue with overloaded address-of operators.

seems like the explicit deepcopy helpers in the control flow state objects are no longer needed but crash the compiler due to infinite recursion

fix crash where Coroutine deallocation could execute Python code to print a warning which could trigger GC and hit the dead Coroutine object

exclude optimised builtin methods from being the Python method call optimisation (previously broke code generation)

disable syntax support for "yield" expressions in function argument annotations and default args which never worked and crashes the compiler

gcc older than 4.7. This fixes a recurring Travis build failure.