gamemode: Add new 'Selection Halo' feature

This feature allows Hiders to easily tell which prop they will turn into if they press Use. As always, it can be fully configured and even turned off. By default it is enabled and set to Approximate mode.

In Approximate mode, the client is responsible for guessing the best match to the Use key, but does not have any actual influence on what they will really turn into. This will in most cases be enough, as the internal Use test relies on the forward vector, which is checked by this mode. For those requiring more accuracy, there is the Accurate mode.

In Accurate mode, the server is responsible for exactly knowing the best match to the Use key and sending this to the user. This has a server performance impact that scales with the player base and the rate at which these updates are performed can be configured. This mode is affected by lag and packet loss, so only really useful for high performance LAN servers or testing.

source/gamemodes/prophuntextended/prophuntextended.txt

@@ -371,5 +371,31 @@
 			"help"		"Camera: Maximum Camera Lag."
 		}
 		
+		// Selection Halo
+		900
+		{
+			"name"		"ph_selectionhalo_allow"
+			"text"		"Selection Halo Allowed"
+			"type"		"CheckBox"
+			"default"	"1"
+			"help"		"Selection Halo: Allow clients to enable halo around the currently looked at prop?"
+		}
+		901
+		{
+			"name"		"ph_selectionhalo_approximate"
+			"text"		"Selection Approximate Mode"
+			"type"		"CheckBox"
+			"default"	"1"
+			"help"		"Selection Halo: Enable approximate selection halo, which only checks the forward vector on the client."
+		}
+		902
+		{
+			"name"		"ph_selectionhalo_interval"
+			"text"		"Selection Halo Allowed"
+			"type"		"Numeric"
+			"default"	"0.05"
+			"help"		"Selection Halo: Interval for updates of the accuracte selection halo in seconds."
+		}
+		
 	}
 }