Do not trigger Ctrl-Tab handling when pressing Ctrl-Shift-Tab

Previously, the keybinding for Ctrl-Tab didn't check the status of the
Shift key, so it would also trigger when pressing Ctrl-Shift-Tab. This
resulted in switching tabs forward *and* back, making it look like the
switch back was not working.

Closes: #195

Author: matthijskooijman

app/src/processing/app/EditorListener.java

@@ -44,12 +44,11 @@ public void keyPressed(KeyEvent event) {
     int code = event.getKeyCode();
 
     // Navigation..
-    if ((event.getModifiers() & CTRL) == CTRL && code == KeyEvent.VK_TAB) {
+    if ((event.getModifiers() & CTRL_SHIFT) == CTRL && code == KeyEvent.VK_TAB) {
       sketch.handleNextCode();
     }
 
     // Navigation..
-    // FIXME: not working on LINUX !!!
     if ((event.getModifiers() & CTRL_SHIFT) == CTRL_SHIFT && code == KeyEvent.VK_TAB) {
         sketch.handlePrevCode();
     }