Add external project LDC to release notes.

LDC, the LLVM-based D compiler, is already ready for LLVM 9.0.0.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_90@372167 91177308-0d34-0410-b5e6-96231b3b80d8

Author: redstar

docs/ReleaseNotes.rst

@@ -349,6 +349,21 @@ LLD combined with lazily building compiler-rt to provide out-of-the-box
 cross-compiling for all supported targets.
 
 
+LDC - the LLVM-based D compiler
+-------------------------------
+
+`D <http://dlang.org>`_ is a language with C-like syntax and static typing. It
+pragmatically combines efficiency, control, and modeling power, with safety and
+programmer productivity. D supports powerful concepts like Compile-Time Function
+Execution (CTFE) and Template Meta-Programming, provides an innovative approach
+to concurrency and offers many classical paradigms.
+
+`LDC <http://wiki.dlang.org/LDC>`_ uses the frontend from the reference compiler
+combined with LLVM as backend to produce efficient native code. LDC targets
+x86/x86_64 systems like Linux, OS X, FreeBSD and Windows and also Linux on ARM
+and PowerPC (32/64 bit). Ports to other architectures are underway.
+
+
 Additional Information
 ======================