Rewrite the Register module

It was getting increasingly convoluted and incomprehensible.
Now uses the Program.HcPkg and Program.Scripts modules.

Distribution/Simple.hs

@@ -95,7 +95,7 @@ import Distribution.Simple.Command
 import Distribution.Simple.Build        ( build )
 import Distribution.Simple.SrcDist      ( sdist )
 import Distribution.Simple.Register
-         ( register, unregister, removeRegScripts )
+         ( register, unregister )
 
 import Distribution.Simple.Configure
          ( getPersistBuildConfig, maybeGetPersistBuildConfig
@@ -385,9 +385,6 @@ clean pkg_descr flags = do
       exists <- doesDirectoryExist distPref
       when exists (removeDirectoryRecursive distPref)
 
-    -- these live in the top level dir so must be removed separately
-    removeRegScripts
-
     -- Any extra files the user wants to remove
     mapM_ removeFileOrDirectory (extraTmpFiles pkg_descr)
 

Distribution/Simple/Configure.hs

@@ -107,8 +107,6 @@ import Distribution.Simple.Utils
     , intercalate, comparing, cabalVersion, cabalBootstrapping
     , withFileContents, writeFileAtomic 
     , withTempFile )
-import Distribution.Simple.Register
-    ( removeInstalledConfig )
 import Distribution.System
     ( OS(..), buildOS, buildArch )
 import Distribution.Version
@@ -403,8 +401,6 @@ configure (pkg_descr0, pbi) cfg
                          | (name, uses) <- inconsistencies
                          , (pkg, ver) <- uses ]
 
-        removeInstalledConfig distPref
-
         -- installation directories
         defaultDirs <- defaultInstallDirs flavor userInstall (hasLibs pkg_descr)
         let installDirs = combineInstallDirs fromFlagOrDefault