Update containers submodule to v0.5.7.1 release tag

This is the new designated release to go with GHC 8.0.1

This is only a meta-data change relative to v0.5.7.0

/cc @foxik

containers @ d08e47bf

-Subproject commit d86ba69819e716d9ee021cf3b34ba7244f2e1649
+Subproject commit d08e47bf6895da8c8b5a7dd62496a2f4fe73631e

testsuite/tests/driver/T10970.stdout

-0.5.7.0
+0.5.7.1
 OK

testsuite/tests/package/package01e.stderr

 
 package01e.hs:2:1: error:
     Failed to load interface for ‘Data.Map’
-    It is a member of the hidden package ‘containers-0.5.7.0’.
+    It is a member of the hidden package ‘containers-0.5.7.1’.
     Use -v to see a list of the files searched for.
 
 package01e.hs:3:1: error:
     Failed to load interface for ‘Data.IntMap’
-    It is a member of the hidden package ‘containers-0.5.7.0’.
+    It is a member of the hidden package ‘containers-0.5.7.1’.
     Use -v to see a list of the files searched for.

testsuite/tests/th/TH_Roles2.stderr

@@ -6,7 +6,7 @@ TYPE CONSTRUCTORS
 COERCION AXIOMS
 Dependent modules: []
 Dependent packages: [array-0.5.1.0, base-4.9.0.0, binary-0.8.0.0,
-                     bytestring-0.10.7.0, containers-0.5.7.0, deepseq-1.4.2.0,
+                     bytestring-0.10.7.0, containers-0.5.7.1, deepseq-1.4.2.0,
                      ghc-boot-0.0.0.0, ghc-prim-0.5.0.0, integer-gmp-1.0.0.0,
                      pretty-1.1.3.2, template-haskell-2.11.0.0]