streamline non-C-function fallback code for the 1-arg call case to avoid overhead beyond the type checks

simplify WithTargetAssignmentStatNode and make it more robust against replacements of the context manager node; undo node.result() checking as it broke TempNode's disposal code

when replacing SimpleCallNode with PyMethodCallNode, make sure we replace all cloned references to the node, not only the current one

--HG--
extra : amend_source : a1b27560de97695dde4b9fea41a39f7f10de736c

--HG--
extra : transplant_source : %E7%F6%F6%0F%80%3A%B2%BDs%7E%8D%80p%2AYX%3B%08%DBL

Mark PyErr_SetInterrupt as nogil

speed up method calls a little by inlining CPython's method_call() and avoiding duplicate args tuple packing

--HG--
extra : amend_source : 52480a79feadc93a60bdeee1837a31bf3539b327

Added PyPy 3 to the build matrix

add "meteor_contest" benchmark as demo of a program that Cython cannot speed up very much as the bulk of the work (set operations) is in CPython's own code

Use all distutils config files in pyximport