[docs] Mention opt -metarenamer in the bugpoint docs

Thanks to arsenm and davide for the suggestion!

llvm-svn: 318318
diff --git a/llvm/docs/Bugpoint.rst b/llvm/docs/Bugpoint.rst
index 3327c02..27732e0 100644
--- a/llvm/docs/Bugpoint.rst
+++ b/llvm/docs/Bugpoint.rst
@@ -151,8 +151,10 @@
   optimizations to be randomized and applied to the program. This process will
   repeat until a bug is found or the user kills ``bugpoint``.
 
-* ``bugpoint`` can produce IR which contains long names. To simplify the names,
-  run ``opt -strip -instnamer`` over the IR.
+* ``bugpoint`` can produce IR which contains long names. Run ``opt
+  -metarenamer`` over the IR to rename everything using easy-to-read,
+  metasyntactic names. Alternatively, run ``opt -strip -instnamer`` to rename
+  everything with very short (often purely numeric) names.
 
 What to do when bugpoint isn't enough
 =====================================