Pyobjc

* Updated for the macOS 10.15.1 SDK (Xcode 11.2)

* Fix reference counting in -[OC_PythonData length], which resulted
in use-after-free.

* 281: Fix problems found in pyobjc-core by the clang static analyser

* 277: Remove debug print accidently left in production

* 278: Surpress "-Wunguarded-availability" warnings in the extension
AppKit._inlines

* Removed Python 2 support from the C extension in pyobjc-core

* Reformatted code in pyobjc-core:

- Use "black" for Python code
- Use "clang-format" for Objective-C code

As a side-effect of this all usage of "NS_DURING" and "PyObjC_DURING"
has been replaced by the expansion of those macros, mostly because
"clang-format" doesn't understand these kinds of blocks.

Replacing "PyObjC_DURING" by its expansion also reduces the knowledge
needed to understand what's going on w.r.t. the Python GIL.

The macro "PyObjC_DURING", and its siblings, have been removed as well.

* Updated bindings for macOS 10.15 (Xcode 11.0)

* The userspace driver frameworks introduced in macOS 10.15
(DriverKit and related frameworks) will not be exposed through
PyObjC. Please let me know if you have a good
use case for using these frameworks with Python.

* Add new framework wrappers for all other new frameworks
in macOS 10.15:

- AuthenticationServices
- CoreHaptics
- CoreMotion
- DeviceCheck
- ExecutionPolicy
- FileProvider
- FileProviderUI
- LinkPresentation
- OSLog
- PencilKit
- PushKit
- QuickLookThumbnailing
- Speech
- SoundAnalysis
- SystemExtensions

* Add new framework wrappers for a number of older
frameworks:

- MetalKit (new in macOS 10.11)

* Issue 271: Fix crash when creating NSData objects on macOS 10.15

* PR 21: Switch xcodebuild invocation to xcrun for sdk path

Patch by Clément Bouvier

* 271: Fix crash when creating NSData objects on macOS 10.15

* Fix compile error on macOS 10.15

* Updated metadata for Xcode 10.2

* 252: ``objc.registerStructAlias`` no longer emits a deprecation
warning because it is still used by the framework wrappers.

The function is still deprecated though, the deprecation will reappear
once the metadata has been updatd.

* 75: The core bridge now uses :func:`PyDict_GetItemWithError`, which
may result in exceptions being raised that were previously swallowed.

* 247: Partially switch to the new buffer API instead of the older
Python 2 buffer API.

The new implementation is more correct, but may keep Python objects
alive longer than the previous implementation, and also affects
buffer related functionality of Python objects. In particular, calling
``[someData bytes]`` on a Python object keeps the ``Py_buffer`` alive
until the next flush of the autoreleasepool.

* 257: Fix incorrect metadata for the callback argument to
``-[AVCaptureStillImageOutput captureStillImageAsynchronouslyFromConnection:completionHandler:]``.

258: Add bindings to the "PrintCore" APIs from the ApplicationServices framework.

* Python 2: UserDict.UserDict instances are now bridged to instances of
a subclass of NSDictionary.

* 254: Fix compile error on macOS 10.9 or earlier

* 255: Calling completion handler failed due to incomplete runtime info

PyObjC's metadata system didn't automaticly set the call signature
for blocks passed into a method implemented in Python. This causes problems
when the ObjC or Swift block does not have signature information in the
ObjC/blocks runtime.

* Use MAP_JIT when allocating memory for the executable stubs for Python
methods.

With the "restricted" runtime you'll have to add the "com.apple.security.cs.allow-jit"
entitlement to use this flag, in earlier versions you'd have to use
a different entitlement: "com.apple.security.cs.allow-unsigned-executable-memory".

The MAP_JIT flag is only used on macOS 10.14 or later.

* Ensure that PyObjC can be built using /usr/bin/python on macOS 10.14

This failed due the problems with header files in the SDK included with Xcode 10.