Remove the BBVectorize pass.

It served us well, helped kick-start much of the vectorization efforts
in LLVM, etc. Its time has come and past. Back in 2014:
http://lists.llvm.org/pipermail/llvm-dev/2014-November/079091.html

Time to actually let go and move forward. =]

I've updated the release notes both about the removal and the
deprecation of the corresponding C API.

llvm-svn: 306797
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index 5939805..ddb31ac 100644
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -54,8 +54,9 @@
   its nature as a general purpose PDB manipulation / diagnostics tool that does
   more than just dumping contents.
   
-
-* ... next change ...
+* The ``BBVectorize`` pass has been removed. It was fully replaced and no
+  longer used back in 2014 but we didn't get around to removing it. Now it is
+  gone. The SLP vectorizer is the suggested non-loop vectorization pass.
 
 .. NOTE
    If you would like to document a larger change, then you can add a
@@ -111,7 +112,11 @@
 Changes to the C API
 --------------------
 
- During this release ...
+* Deprecated the ``LLVMAddBBVectorizePass`` interface since the ``BBVectorize``
+  pass has been removed. It is now a no-op and will be removed in the next
+  release. Use ``LLVMAddSLPVectorizePass`` instead to get the supported SLP
+  vectorizer.
+
 
 External Open Source Projects Using LLVM 5
 ==========================================