add BspDemo.bsp data file

add sphere2.urdf
move btSpatialAlgebra into LinearMath
remove some warnings, introduce BT_ZERO, BT_ONE, BT_HALF as defines for 0.f/0., 1.f/1., 0.5f/0.5 respectively

test/hello_gtest/premake4.lua

@@ -12,6 +12,11 @@
 		".","../gtest-1.7.0/include"
 	}
 
+	if os.is("Windows") then
+		--see http://stackoverflow.com/questions/12558327/google-test-in-visual-studio-2012
+		defines {"_VARIADIC_MAX=10"}
+	end
+	
 --        linkLib "gtest"			
 	links "gtest"