Couple of small optimisation

Add option to build for gprof
Do not build by default with the renderstat (they have a reasonable impact on performances)
Separated created ray and castedray in the stats
Trying to force some simple function to be inlined

source/camera.cpp

@@ -54,6 +54,7 @@ Ray Camera::rayForPixel(uint32_t pixelX, uint32_t pixelY)
     Tuple origin = this->inverseTransform * Point(0, 0, 0);
     Tuple direction = (pixel - origin).normalise();
 
+    stats.addCastedRay();
     return Ray(origin, direction);
 }