Restore click-stacking on syringes

[aloe]

I think this is already the behavior? Syringe action bars don’t seem to interrupt on click or on starting another action; just when being attacked, moving, or being stunned.
As far as I know clicking 3 times should still work; the latter 2 actions will fill up “behind” the first action bar.
If it indeed doesn’t let you inject 15u via successive clicks then it’s a bug, I think.