$docdev fixups: mostly to avoid empty output

... after auto-removing some kinds of files by default.
In some cases I let them be removed and in others I let them be put into
$docdev. That was more due to general indecisiveness on this question
than any reasons in the particular cases.

pkgs/development/perl-modules/generic/default.nix

@@ -4,7 +4,7 @@ perl:
 
 perl.stdenv.mkDerivation (
   {
-    outputs = [ "out" "man" ];
+    outputs = [ "out" "docdev" ];
 
     doCheck = true;