[commit: ghc] ghc-8.4: Bump xhtml submodule to 3000.2.2.1 (597ba9c)

[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/597ba9c012d27f3a2695e6e09aafe8abb4f51c36/ghc

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

commit 597ba9c012d27f3a2695e6e09aafe8abb4f51c36
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Mon Mar 26 17:06:18 2018 -0400

    Bump xhtml submodule to 3000.2.2.1


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597ba9c012d27f3a2695e6e09aafe8abb4f51c36
 libraries/xhtml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/xhtml b/libraries/xhtml
index c5c623e..721779a 160000
--- a/libraries/xhtml
+++ b/libraries/xhtml
@@ -1 +1 @@
-Subproject commit c5c623e497f13ec187e0d228e0e8a3d9ee39a715
+Subproject commit 721779acc35dccd6a43a292b24099b65d93d390c