Update pxMultiActor.cpp

Fixed PhysX compile issue on VS2010 ("'FS' : is not a class or namespace name")

In reference to http://www.garagegames.com/community/forums/viewthread/135499
Default value for WaterFogData plane distance

Set the default WaterFogData plane distance to be the same as global
bounds.  This solves an issue with the connection's control object
mistakenly thinking it is under a water plane in a debug build.
Merge pull request #520 from DavidWyand-GG/CausticsFix

Default value for WaterFogData plane distance
Underwater Fixes

- Caustics now respects the passed in water plane rather than assume
that the water plane is on the XY plane.  This allows for caustics to
work for steep rivers.
- Fixed lerp() warning in underwaterFogP.hlsl.
- Cleaned up turbulence and caustics PostEffect scripts to remove unused
items.
- Caustics are now enabled and disabled based on the control object
being underwater, just like turbulence.  Moved this code to fog.cs to be
with the underwater postFX.
Merge pull request #521 from DavidWyand-GG/CausticsFix

Underwater Fixes
Merge pull request #518 from robertsim007/patch-1

Update pxMultiActor.cpp (fixed)