[commit: ghc] master: Update stm submodule to v2.4.4.1 release (6eabd93)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/6eabd93d3cfaffab838830cf9a2618565ff04254/ghc

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

commit 6eabd93d3cfaffab838830cf9a2618565ff04254
Author: Herbert Valerio Riedel <hvr at gnu.org>
Date:   Tue Dec 22 13:59:36 2015 +0100

    Update stm submodule to v2.4.4.1 release
    
    This `stm` release also addresses #10967


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

6eabd93d3cfaffab838830cf9a2618565ff04254
 libraries/stm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/stm b/libraries/stm
index 9870cf1..b49b506 160000
--- a/libraries/stm
+++ b/libraries/stm
@@ -1 +1 @@
-Subproject commit 9870cf156e5e7e21785b236da41f2466bf9f4b29
+Subproject commit b49b5060d5e78a9ee2fa6a069a7195654ebdf08a