Preparation to VideoTexture: everything but the VideoTexture module itself.

Rename PHY_GetActiveScene() to KX_GetActiveScene(): more logical name
Add KX_GetActiveEngine()

new KX_KetsjiEngine::GetClockTime(void) to return current 
render frame time: if the CPU does not keep up with the 
frame rate, up to 5 consecutive logic frames are processed 
between each render frame, so that the logic system stays 
accurate even if the graphic system is slow. For the video 
texture module, it is important to stay in sync with the
render frame: no need to update the texture for logic frame.

BL_Texture::swapTexture(): texture id manipulation
BL_Texture::getTex() : return material texture

Enable video support in ffmpeg for Linux.

source/gameengine/Ketsji/KX_PythonInit.cpp

@@ -1461,16 +1461,21 @@ PyObject* initMathutils()
 	return Mathutils_Init("Mathutils"); // Use as a top level module in BGE
 }
 
-void PHY_SetActiveScene(class KX_Scene* scene)
+void KX_SetActiveScene(class KX_Scene* scene)
 {
 	gp_KetsjiScene = scene;
 }
 
-class KX_Scene* PHY_GetActiveScene()
+class KX_Scene* KX_GetActiveScene()
 {
 	return gp_KetsjiScene;
 }
 
+class KX_KetsjiEngine* KX_GetActiveEngine()
+{
+	return gp_KetsjiEngine;
+}
+
 // utility function for loading and saving the globalDict
 int saveGamePythonConfig( char **marshal_buffer)
 {