Add 1.9 release announcement to 2.x series.

ANNOUNCE.1.9

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+GNUstep Objective-C Runtime 1.9
+===============================
+
+This the ninth official release of the GNUstep Objective-C runtime (a.k.a.
+libobjc2).  This runtime was designed to support the features of modern
+dialects of Objective-C for use with GNUstep and other Objective-C programs.
+Highlights of this release include:
+
+- Support for 64-bit ARM (AArch64) processors, including assembly fast paths
+  for message sending.
+
+- Improved the dispatch table representation to improve performance and cache
+  usage on the fast path.
+
+- The implementation of `imp_implementationWithBlock`, the function that allows
+  blocks to be used as methods, no longer requires physical pages to be mapped
+  both writeable and executable.
+
+- Numerous improvements to the interaction between runtime functions and ARC.
+
+- Support for Thumb-2 interworking on ARM.  Note that the library must be
+  compiled for ARMv7 or ARMv6T2 for this code to be enabled.  Once it has been,
+  other Objective-C binaries linked with the library can be compiled as ARM or
+  Thumb-2 code.  This will also generate Thumb-2 message send functions,
+  improving instruction cache usage.
+
+- Significant improvements to ARC, including
+
+  * The runtime no longer acquires a global lock on every object deallocation (a
+    global lock is still used for objects that have weak references). *NOTE:*
+    This is incompatible with other code directly inspecting the reference
+    count and will break with older versions of GNUstep Base!
+
+  * Weak references use a scheme closer to C++ `std::weak_pointer` and are
+    lazily zeroed on access.  This reduces the space overheads for weak
+    references.
+
+  * Some additional helper functions are added for use in `NSObject` and other
+    root classes,  which simplifies the layering between the runtime and the
+    Foundation (or equivalent) implementation.
+
+- Improvements to how the runtime handles layout of ivars with strong alignment
+  requirements, which should fix issues relating to using vector types in
+  Objective-C objects.
+
+- The option to build a separate libobjcxx has been removed.  The runtime will
+  now depend on the C++ standard library implementation if no useable C++
+  runtime is available.  Note that C++ exception interworking does not work
+  because LLVM's libc++abi (shipped by Apple) does not provide GNU-compatible
+  hooks and so Objective-C++ exception support will be automatically disabled
+  on this platform.  Any other platforms shipping libc++abi should consider
+  either GNU libsupc++ or libcxxrt as an alternative.
+
+You may obtain the code for this release from git and use the 1.9 branch:
+
+https://github.com/gnustep/libobjc2.git
+
+Alternatively, a tarball is available from:
+
+https://github.com/gnustep/libobjc2/archive/v1.9.zip
+https://github.com/gnustep/libobjc2/archive/v1.9.tar.gz
+
+The runtime library is responsible for implementing the core features of the
+object model, as well as exposing introspection features to the user.  The
+GNUstep runtime implements Apple's Objective-C Runtime APIs, and a small number
+of GCC APIs for legacy compatibility.
+
+This library is based on the Étoilé Objective-C Runtime, an earlier research
+prototype, and includes support for non-fragile instance variables,
+type-dependent dispatch, and object planes.  It is fully backwards compatible
+with the FSF's GCC 4.2.1 Objective-C ABI and also implements a new ABI that is
+supported by Clang and Étoilé's LanguageKit and is required for some of the
+newer features.
+
+If you come across any problems, please file them in the issue tracker:
+
+https://github.com/gnustep/libobjc2/issues