b=821749 remove code to give transient-for-none dialogs a separate ICCCM group leader r=roc

This reverts the change for bug 194323, which is now no longer necessary.
Removing this means that the GtkWindow is realized with its event mask set and
oxygen-gtk knows to keep out of our way.

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extra : transplant_source : %81%A4%C3o%A7%EF%91y%B8%E2%B1%FE%A9%F3v/%0A%CF%2A-
b=821749 remove mWindowGroup, handled by gtk_window_set_transient_for r=roc

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extra : transplant_source : %AF%E2%D5_h%7B%2A%B2%BCQ%88%CD%1E%DEfq%E7%3B%3E%04
b=821749 remove unnecessary mTransientParent r=roc

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extra : transplant_source : %D9E%BD%F12%0E%B8U%EB%98%D3%B4%CD%D4%AC/%E5%A9%A6%05
b=623380 destroy XtClient child window on unrealize r=stransky

--HG--
extra : transplant_source : u%8A%02%E1%C5%96%16%21ica%9A%80%AF%A3e%16%0C%7Dy