optimize general sorted(x) calls

fix shrinking and overflow in cpython.array

optimize sorted([a,b,c]) into PyList_Sort call

Emit DL_IMPORT macro for python3

implement PEP 479: replace accidental StopIteration exceptions that exit the generator body by RuntimeError

fix temp leak and crash when assigning a C value to both a Python and C target in a cascaded assignment

clean up regular expression in parser (not problematic as it only matches what the scanner already accepted)

cannot currently enable warning checks for C++ class definition syntax as there are incorrect warnings

extend C++ tests to make sure we do not generate warnings (and fix some warnings that we did generate)

tighten Python-to-C++-reference warning to apply only to C++ classes as target and do not show it by default (usage might be legitimate and/or enforced by an external API)

Generate warning when Python object is used as C++ container reference parameter.