[coroutines] Part 3 of N: Adding Boilerplate for Coroutine Passes

This adds boilerplate code for all coroutine passes,
the passes are no-ops for now.
Also, a small test has been added to verify that passes execute in
the expected order or not at all if coroutine support is disabled.

Patch by Gor Nishanov!

Differential Revision: https://reviews.llvm.org/D22847

llvm-svn: 277033
diff --git a/llvm/docs/Coroutines.rst b/llvm/docs/Coroutines.rst
index 4fbdabf..30be4e7 100644
--- a/llvm/docs/Coroutines.rst
+++ b/llvm/docs/Coroutines.rst
@@ -1177,8 +1177,8 @@
 Upstreaming sequence (rough plan)
 =================================
 #. Add documentation.
-#. Add coroutine intrinsics.  <= we are here
-#. Add empty coroutine passes.
+#. Add coroutine intrinsics.
+#. Add empty coroutine passes.  <= we are here
 #. Add coroutine devirtualization + tests.
 #. Add CGSCC restart trigger + tests.
 #. Add coroutine heap elision + tests.