more explicit indication of bundled jdk, which is required for newer versions of JavaAppLauncher;

--- a/Admin/MacOS/Info.plist-part1	Wed Sep 16 20:54:41 2015 +0200
+++ b/Admin/MacOS/Info.plist-part1	Wed Sep 16 21:26:37 2015 +0200
@@ -35,7 +35,7 @@
 <key>NSSupportsAutomaticGraphicsSwitching</key>
 <string>true</string>
 <key>JVMRuntime</key>
-<string>jdk</string>
+<string>bundled.jdk</string>
 <key>JVMMainClassName</key>
 <string>isabelle.Main</string>
 <key>CFBundleDocumentTypes</key>

--- a/Admin/lib/Tools/makedist_bundle	Wed Sep 16 20:54:41 2015 +0200
+++ b/Admin/lib/Tools/makedist_bundle	Wed Sep 16 21:26:37 2015 +0200
@@ -376,7 +376,7 @@
         cp -R "$APP_TEMPLATE/Resources/." "$APP/Contents/Resources/."
 
         ln -sf "../Resources/${ISABELLE_NAME}/contrib/jdk/x86_64-darwin" \
-          "$APP/Contents/PlugIns/jdk"
+          "$APP/Contents/PlugIns/bundled.jdk"
 
         cp macos_app/JavaAppLauncher "$APP/Contents/MacOS/." && \
           chmod +x "$APP/Contents/MacOS/JavaAppLauncher"