Units disappear if ungarissoned too fast

[vts]

If several units are garrisoned inside a building and you ungarrison them all individually by clicking the unload button really fast, units are sometimes lost. The number of units that is garrisoned does not seem to matter, as I have observed it to happen even for 2 units.

To reproduce:

• Start a new singleplayer game on Gallic Fields.
• Select more than 2 of the starting units and garrison them in the Palisade Fort closest to the camera.
• Select the palisade fort, set a rally point, and keep hitting the single-unit unload button as fast as you can.
• Observe how fewer units exit the fort than were originally garrisoned.

[ben]

(In [10192]) Fixes garrisoned units disappearing when eject occurs too frequently. See #910.

[historic_bruno]

OK, submitted a fix for the really bad part of this bug, you'll just have to click a little more slowly now, but nothing will disappear :)

The problem is after successfully ejecting a unit, there is still a short time when the UI is bound to the old garrison state and this button happens to reference the unit previously ejected. Now the simulation will check and give an error message. I'm not sure how to fix this on the UI side to really fix this, maybe putting a delay in how fast you can click the button, one click per GUI tick.

[Deiz]

In 12443:

Added support for ungarrisoning units by template name and for ungarrisoning from multiple entities at once. Fixes #910.

[elexis]

In 19910:

Remove unused function (from rP8451) after the only call to it was removed in rP12443.

Refs #910, D736
Discussed with: Deiz, bb