bash: change shell script option types from string to lines

installation-cd-base: export mountPoint=/mnt. This doesn't change the default behavior, but an explicit
mount point specification is cleaner.

modules/installer/cd-dvd/installation-cd-base.nix

@@ -32,4 +32,6 @@ with pkgs.lib;
   # To speed up installation a little bit, include the complete stdenv
   # in the Nix store on the CD.
   isoImage.storeContents = [ pkgs.stdenv pkgs.busybox ];
+
+  environment.shellInit = "export mountPoint=/mnt";
 }

modules/programs/bash/bash.nix

@@ -46,7 +46,7 @@ let
       description = ''
         Shell script code used to initialise the shell prompt.
       '';
-      type = with pkgs.lib.types; string;
+      type = with pkgs.lib.types; lines;
     };
 
     environment.shellInit = mkOption {
@@ -55,7 +55,7 @@ let
       description = ''
         Shell script code called during login shell initialisation.
       '';
-      type = with pkgs.lib.types; string;
+      type = with pkgs.lib.types; lines;
     };
 
     environment.interactiveShellInit = mkOption {
@@ -64,7 +64,7 @@ let
       description = ''
         Shell script code called during interactive shell initialisation.
       '';
-      type = with pkgs.lib.types; string;
+      type = with pkgs.lib.types; lines;
     };
 
     environment.enableBashCompletion = mkOption {