Enable the NumPy 1.7 API macro in all NumPy integration tests that do not rely on deprecated C-API internaly.

Closes #2621.

Closes #2621.

Prevent assigned global variables from being marked and treated as closure variables in generators and coroutines.
Closes #2613.

Fix lambdas/genexpr in @cfunc functions

Clean up directives to distinguish between those that belong to a function or class and those that are generally inherited. Everything that is not inherited should also not have a default value and instead exist or not.
Then, prevent lambdas and generator expressions from inheriting directives from their outer function/scope, e.g. "@cython.cdef".
Closes #459.

Closes #2616.

Check some child nodes against the correct nogil context when they are actually being evaluated in the outer scope (e.g default arguments or annotations of a nogil function).

Discard invisible type annotations from cdef functions after applying them, as they might get in the way of @nogil declarations etc.

Fixes Github issue #2603.

This provides a test case for #2603

Warn when no "language_level" is specified.

Closes #2593.

Also removes the usage of the header file "long.cpp" which was removed in Pythran 0.8.7.

Use exception stack in Py3.7