Add support for checking Haskell code via a wrapper script which can be used for other tools, and fix a readline problem with the DMD wrapper script.

plugin/ale/util.vim

@@ -0,0 +1,18 @@
+if exists('g:loaded_ale_util')
+    finish
+endif
+
+let g:loaded_ale_util = 1
+
+function! s:FindWrapperScript()
+    for parent in split(&runtimepath, ',')
+        " Expand the path to deal with ~ issues.
+        let path = expand(parent . '/' . 'stdin-wrapper')
+
+        if filereadable(path)
+            return path
+        endif
+    endfor
+endfunction
+
+let g:ale#util#stdin_wrapper = s:FindWrapperScript()