Disable GC during hacked calls to PyType_Ready() that simulate a heap type for an actual non-heap type, because it can lead to crashes if GC visits such a hacked type.
Closes https://github.com/cython/cython/issues/3603

Reduce the code overhead of the memoryview implementation a little by disabling CyFunctions for its methods.

Reduce the code overhead of exception raising in generated Cython code and the memoryview code by avoiding explicit calls to create the exception and prepared constant argument tuples. "raise Exc, message" can do this implicitly.

Move less common ref-counting cases for memory views out of the fast-path and only look up the atomic acquisition count value once per INC/DEC operation.

When it's merged into the main module, wrap it in a CompilerDirectivesNode.

Also mark the case of an uninitialised memory view slice as "unlikely()" when refcounting it since it's most probably not a performance critical case.

Mark the last deletion of a memory view slice as "unlikely()" to ask the C compiler to optimise for the repeated re-use case (usually in loops).

Mark the first creation of a memory view slice as "unlikely()" to ask the C compiler to optimise for the repeated re-use case (usually in loops).

Fix up the NumPy warnings hack by using the actual "import_array()" function declaration instead of a wrong one.

Also mark the case of an uninitialised memory view slice as "unlikely()" when refcounting it since it's most probably not a performance critical case.

Mark the last deletion of a memory view slice as "unlikely()" to ask the C compiler to optimise for the repeated re-use case (usually in loops).

Mark the first creation of a memory view slice as "unlikely()" to ask the C compiler to optimise for the repeated re-use case (usually in loops).

Closes https://github.com/cython/cython/issues/3594

Closes https://github.com/cython/cython/issues/1462

Move the work directory of the examples tests into an 'examples/' subdirectory to get it out of the way of the other test types.

Move the work directory of the examples tests into an 'examples/' subdirectory to get it out of the way of the other test types.