Experimental fix for tilted avatar capsule, Mantis #2905

Set av_capsule_tilted to false in opensim.ini. Default is true, so there is
no change in avatar behavior (and no breaking of existing content which
relies on the tilted capsule).

This commit straightens up the avatar capsule so it behaves consistently
(e.g. same collision behavior against prims regardless of which direction
the avatar is coming from; ability to fit through narrow doorways).

Please note this introduces other side effects which have not been fixed.
In particular:

* The avatar frequently falls through the terrain if it is not flat, though
the avatar behaves pretty well on flat terrain. This requires investigation
of the ode terrain collider.
* The apparent foot position of the avatar with respect to the ground
is changed. This requires investigation of the avatar height/capsule height.

Please consider this as work in progress.

bin/OpenSim.ini.example

@@ -473,6 +473,10 @@
     av_capsule_standup_tensor_win = 550000
     av_capsule_standup_tensor_linux = 550000
 
+    ; specifies if the capsule should be tilted (=true; old compatibility mode)
+    ; or straight up-and-down (=false; better and more consistent physics behavior)
+    av_capsule_tilted = true
+
     ; used to calculate mass of avatar.
     ; float AVvolume = (float) (Math.PI*Math.Pow(CAPSULE_RADIUS, 2)*CAPSULE_LENGTH);
     ; av_density * AVvolume;