Caret is gone after switching applications via taskbar

[yonojoy]

I tested with the demo application under Win7 (compiled with XE4).

Steps to reproduce:

• start demo application
• enter "test" into the edit field
• switch to another application via taskbar
• switch back to demo by clicking the icon on the taskbar
  BUG: caret is gone (but edit correctly has the focus and accepts keystrokes)

I think the problem is, that the WM_ACTIVATE message, that gets send to the VCL form, should somehow set Active of the wrapped FMX form (which does not seem to work).

[yonojoy]

An other situation when the carret gets lost can be reproduced in the following way:

• Compile and start the demo applicaiton
• Click into the FMX edit field
• Enter a
• Press the tab key
• Press SHIFT+TAB to return to the edit
  --> caret is gone

But I think this has another cause therefor I added issue #15