[commit: ghc] ghc-8.4: Bump stm submodule to v2.4.5.1 (8c857df)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-8.4
Link       : http://ghc.haskell.org/trac/ghc/changeset/8c857df21ebd56ea2464f8808c2381a9889ccb9e/ghc

>---------------------------------------------------------------

commit 8c857df21ebd56ea2464f8808c2381a9889ccb9e
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Fri Oct 5 17:36:32 2018 -0400

    Bump stm submodule to v2.4.5.1


>---------------------------------------------------------------

8c857df21ebd56ea2464f8808c2381a9889ccb9e
 libraries/stm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/stm b/libraries/stm
index 5ea70d4..3722e83 160000
--- a/libraries/stm
+++ b/libraries/stm
@@ -1 +1 @@
-Subproject commit 5ea70d4e15d461888866796a164bf9c177a1e8b8
+Subproject commit 3722e83b92e947d6715153811f16c505c05a54f1