more careful quoting for the sake of Windows;

--- a/src/Pure/System/isabelle_process.scala	Sun Feb 14 13:15:59 2016 +0100
+++ b/src/Pure/System/isabelle_process.scala	Sun Feb 14 13:23:12 2016 +0100
@@ -17,7 +17,8 @@
     val system_process =
       try {
         val script =
-          "\"$ISABELLE_PROCESS\" -P " + system_channel.server_name +
+          File.shell_quote(Isabelle_System.getenv_strict("ISABELLE_PROCESS")) +
+            " -P " + system_channel.server_name +
             (if (prover_args == "") "" else " " + prover_args)
         val process = Bash.process(null, null, false, "-c", script)
         process.stdin.close

--- a/src/Tools/jEdit/src/isabelle_logic.scala	Sun Feb 14 13:15:59 2016 +0100
+++ b/src/Tools/jEdit/src/isabelle_logic.scala	Sun Feb 14 13:23:12 2016 +0100
@@ -74,7 +74,7 @@
     val print_modes =
       (space_explode(',', PIDE.options.string("jedit_print_mode")) :::
        space_explode(',', Isabelle_System.getenv("JEDIT_PRINT_MODE"))).map("-m " + _)
-    (print_modes ::: List("-r", "-q", quote(session_name()))).mkString(" ")
+    (print_modes ::: List("-r", "-q", File.shell_quote(session_name()))).mkString(" ")
   }
 
   def session_start(): Unit = PIDE.session.start("Isabelle", session_args())