Improve player zoom control, doc updates

Players can use sneak and/or aux1 for far-zooming, so they can
far-zoom while treading water in an ocean to look at distant
islands, instead of using the aux1=climb down hack, which causes
all sorts of weird issues with other features that try to detect
movement controls

docs/hopeless.txt

@@ -37,6 +37,11 @@ issue.
 	- Z-fighting against normal nodes; no way to both show inside
 	  surface against air AND avoid z-fighting.
 	- Multiple kinds of water don't "mix"
+	- Because only nodes can produce light, dynamic lights require
+	  use of fake air-like nodes, and because liquids don't mix,
+	  I can't make fake water-like nodes for underwater dynamic
+	  lighting, thus all dynamic lights do NOT work at all
+	  underwater.
 
 - Can't do the sky navigation thing fully
 	- Client resource GC for computed textures could fix the memory

docs/issues-game.txt

@@ -154,13 +154,6 @@ ISSUES-GAME: Gameplay-affecting issues
   down to regular cobble, but it only works with the base node, not the
   etched ones.
 
-- Players losing run speed on damage would be simplified by checking for
-  <max health instead of time of last damage.
-	- Should lose farzoom when damaged too.
-
-- We can reliably detect the zoom player control, make far-zoom only
-  work while zooming, and add hints for it.
-
 - Valleys mapgen rivers seem to rely on having an actual separate
   river water registration with a specific liquid range.
 

docs/issues-hint.txt

@@ -15,5 +15,7 @@ itself.
 
 - Soak-tickling
 
+- Zoom and far-zoom
+
 ........................................................................
 ========================================================================

mods/nc_player_model/api.lua

@@ -122,7 +122,7 @@ nodecore.player_anim = nodecore.player_anim or function(player, data)
 		if mine then data.animcontrol_mine_exp = nodecore.gametime + 0.25 end
 		mine = mine or data.animcontrol_mine_exp and data.animcontrol_mine_exp >= nodecore.gametime
 	end
-	local aux = ctl.aux1
+	local aux = ctl.aux1 and not ctl.zoom
 	if data then
 		if aux then data.animcontrol_aux_exp = nodecore.gametime + 1 end
 		aux = aux or data.animcontrol_aux_exp and data.animcontrol_aux_exp >= nodecore.gametime

mods/nc_player_setup/step_zoomfocus.lua

@@ -11,8 +11,9 @@ nodecore.register_playerstep({
 		label = "zoom focus",
 		action = function(_, data)
 			local ctl = data.control
-			local focusing = ctl.sneak and (not ctl.jump) and (not ctl.up)
-			and (not ctl.down) and (not ctl.left) and (not ctl.right)
+			local focusing = ctl.zoom and (ctl.aux1 or ctl.sneak)
+			and (not ctl.jump) and (not ctl.up) and (not ctl.down)
+			and (not ctl.left) and (not ctl.right)
 			local zoom = zoom_base
 			if focusing and data.zoomfocus then
 				zoom = zoom_base - zoom_base * zoom_ratio * (1 - 1 /