Bump version to 0.5.1.1 and update changelog

array.cabal

 name:          array
-version:       0.5.1.0
+version:       0.5.1.1
 -- NOTE: Don't forget to update ./changelog.md
 license:       BSD3
 license-file:  LICENSE

changelog.md

 # Changelog for [`array` package](http://hackage.haskell.org/package/array)
 
+## 0.5.1.1  *Apr 2016*
+
+  * Bundled with GHC 8.0.1
+  * Use `@since` syntax in Haddock comments
+  * Don't needlessly call `bounds` in `Data.Array.Base.elems` (#10014)
+
 ## 0.5.1.0  *Mar 2015*
 
   * Bundled with GHC 7.10.1