add Vehicles/Hinge2Vehicle demo, based on the ForkLift demo, using btHinge2Constraint with rigid body wheels

change btHinge2Constraint to derive from new btGeneric6DofSpring2Constraint

examples/SimpleOpenGL3/premake4.lua

@@ -0,0 +1,28 @@
+	
+		project "App_SimpleOpenGL3"
+
+		language "C++"
+				
+		kind "ConsoleApp"
+
+  	includedirs {
+                ".",
+                "../../src",
+                ".."
+                }
+
+			
+		links{ "OpenGL_Window","Bullet3Common"}
+		initOpenGL()	
+		initGlew()
+	
+		files {
+		"*.cpp",
+		"*.h",
+		}
+		
+if os.is("Linux") then initX11() end
+
+if os.is("MacOSX") then
+	links{"Cocoa.framework"}
+end