Add some lld-link 9.0 release notes

llvm-svn: 359412

Author: nico

lld/docs/ReleaseNotes.rst

@@ -32,6 +32,17 @@ COFF Improvements
 * lld-link now correctly reports duplicate symbol errors for obj files
   that were compiled with /Gy.
 
+* lld-link now correctly reports duplicate symbol errors when several res
+  input files define resources with the same type, name, and language.
+
+* Undefined symbols are now printed only in demangled form. Pass
+  ``/demangle:no`` to see raw symbol names instead.
+
+* The following flags have been added: ``/functionpadmin``, ``/swaprun:``,
+  ``/threads:no``
+
+* Several speed and memory usage improvements.
+
 * ...
 
 MinGW Improvements