TinyMCE: enter by tab

[Florianer]

Hi guys,
I got a little request for a UI improvement. I can enter the fields like sender and subject by pressing the tab, but I cannot enter the HTML composing TinyMCE field - not sure, but I believe, I can enter the text composing field by tab. Guess, this is only a little modification and hope it will make it soon the following svns.

Florian