Exit Button as a Window Display Toggler

[gat]

When the system tray icon is enabled, it would be useful to have the window's exit button (in the upper-right corner of the window) to perform the same functionality that is currently implemented by clicking the S.T.I. This functionality is similar to other programs' (e.g. Transmission, Rhythmbox, & probably others...). I believe that in Transmission line 40 of https://trac.transmissionbt.com/browser ... /tr-icon.c achieves this purpose - I could be wrong here. Also, to have this achieved there would probably have to be a dependence check on whether the S.T.I. has been enabled in the preferences. I assume that there is some final type of variable that handles that.