[PATCH] Make healer UnitAI more proactive

[causative]

Currently, healers are difficult to use. This is due to two problems with their UnitAI.

First, if an idle healer is near a damaged unit, the idle healer will not walk to heal the unit unless the initial distance between them is very short - the healer's LOS, 30. This makes it difficult to position your damaged army so healers will do their job. This patch fixes this by doubling healer LOS to 60. It does not change healer range, which remains 12 before upgrades.

Second, if you select a group of healers and soldiers and attack-move (ctrl + right-click on an empty area) with them, the healers will just march straight at the enemy and not heal anything. This patch fixes this by making healers on attack-move heal any injured allied units they pass.

The second part of the patch does not apply to healers in formation. The reason is, if there is a mixed formation of healers and soldiers, you don't want to issue the entire formation a HEAL command, because the soldiers can't obey it.

To test this patch: open a scenario with enemy units and healers. Let an enemy injure a unit, then move him near the idle healers. They should walk several times their range to heal the injured unit. Then, move the healers far away again, and with the healers selected, ctrl + right-click past the injured unit. They should heal the injured unit instead of walking past him.

[causative]

title should be prefixed with [PATCH]

[elexis]

Thanks for finding the issue and making a patch!

But don't change UnitAI to double the range, just change the template! Also that pair of braces is not needed.