More reliable Shift pressing & releasing

When a shift is not pressed, press it when a TopsyTurvy key is pressed, and keep
it down as long as the TopsyTurvy key is held, too. Release it when the key
toggles off. This fixes the jitter of #1 in the case where the key is pressed
without a modifier.

In the other case, when a TopsyTurvy key is pressed while a Shift is active too,
send a report after releasing the shifts, to make sure we do not jitter here,
either.

Fixes #1.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/Akela/TopsyTurvy.cpp

@@ -83,13 +83,16 @@ namespace Akela {
     // invert the shift state
 
     if (!topsyTurvyModState) {
-      Keyboard.press (Key_LShift.keyCode);
+      if (key_is_pressed (keyState))
+        Keyboard.press (Key_LShift.keyCode);
       handle_key_event (mappedKey, row, col, keyState | TOPSYTURVY);
       Keyboard.sendReport ();
-      Keyboard.release (Key_LShift.keyCode);
+      if (key_toggled_off (keyState))
+        Keyboard.release (Key_LShift.keyCode);
     } else {
       Keyboard.release (Key_LShift.keyCode);
       Keyboard.release (Key_RShift.keyCode);
+      Keyboard.sendReport ();
       handle_key_event (mappedKey, row, col, keyState | TOPSYTURVY);
       Keyboard.sendReport ();