Now that it is possible, use the mangler in IRObjectFile.

A really simple patch marks the end of a lot of yak shaving :-)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202463 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ReleaseNotes.rst

@@ -52,6 +52,9 @@ Non-comprehensive list of changes in this release
   for assembly output as well. The integrated assembler can be disabled with
   the ``-no-integrated-as`` option,
 
+* llvm-ar now handles IR files like regular object files. In particular, a
+  regular symbol table is created for symbols defined in IR files.
+
 .. NOTE
    For small 1-3 sentence descriptions, just add an entry at the end of
    this list. If your description won't fit comfortably in one bullet