Add a new directive 'str_is_str=True'

Add a new directive 'str_is_str=True' that keeps unprefixed string literals and the 'str' builtin type unchanged even when 'language_level=3' is enabled.
See #2565.

TEST: add test for 'binary incompatibility' warning

Deduplicate constant tuples and slices to generate them only once and share them across the entire module.
Closes #2292.

Previously, line tracing code could be generated before the case-statements and thus be ignored at best or rejected by the C compiler.

Use a different constant (PI instead of NAN) in the "import *" test since NAN does not seem to be defined by MSVC.

Call out the different name used for the wrapper

Allow catching both C++ and Python exceptions.

Explicitly call out the different name used for the wrapper `.pyx` file vs. the other C++ sources

As a new user, I was following along and just called the `.pyx` file `Rectangle.pyx` like everything else which was kinda confusing then when in the `wrapping_CPlusPlus/setup.py` there's a `setup(ext_modules=cythonize("rect.pyx"))` and I was thinking that maybe that file was magically created somehow and was miffed.

Hoisted the blurb on why the file name needs to be different without some additional work and worded it in there.

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