disallow quotes in path specifications -- extra paranoia;

--- a/src/Pure/General/path.ML	Sat Jul 21 17:49:22 2012 +0200
+++ b/src/Pure/General/path.ML	Sat Jul 21 21:16:08 2012 +0200
@@ -51,7 +51,7 @@
   | check_elem (chs as ["~"]) = err_elem "Illegal" chs
   | check_elem (chs as ["~", "~"]) = err_elem "Illegal" chs
   | check_elem chs =
-      (case inter (op =) ["/", "\\", ":"] chs of
+      (case inter (op =) ["/", "\\", "$", ":", "\"", "'"] chs of
         [] => chs
       | bads => err_elem ("Illegal character(s) " ^ commas_quote bads ^ " in") chs);
 

--- a/src/Pure/General/path.scala	Sat Jul 21 17:49:22 2012 +0200
+++ b/src/Pure/General/path.scala	Sat Jul 21 21:16:08 2012 +0200
@@ -29,7 +29,8 @@
   private def check_elem(s: String): String =
     if (s == "" || s == "~" || s == "~~") err_elem("Illegal", s)
     else
-      s.iterator.filter(c => c == '/' || c == '\\' || c == '$' || c == ':').toList match {
+      s.iterator.filter(c =>
+          c == '/' || c == '\\' || c == '$' || c == ':' || c == '"' || c == '\'').toList match {
         case Nil => s
         case bads =>
           err_elem ("Illegal character(s) " + commas_quote(bads.map(_.toString)) + " in", s)