[macosx] Absent KeyEvent modifiers for modifier keys

http://java.net/jira/browse/MACOSX_PORT-190 submitted 2011/07/26 by Yuri Nesterenko
Add a KeyListener to a component to print events. Look at the modifiers reported.
Now, if you press Shift+letter, it will be reported correctly as this letter and modifier Shift. However if you press and release just a modifier key, it will NOT have itself reported as a modifier which is error.
For instance, pressing and releasing of Ctrl+Shift will be reported as two pairs of isolated Ctrl and Shift events sans modifiers. Single Meta, Alt, Shift, or Ctrl also will not be reported as it's own modifier.