I don't think dbDesktopWidth or dbDesktopHeight are valid library functions which is why it won't compile. The really puzzling thing is how have these statements got into your Dark Invaders.cpp file? I've checked mine and there is no reference to either of these statements in any of the files (nor in the documentation file). In the Dark Invaders.cpp file on my system, line 138 (where the error occurs) says playerReset(); and it is inside a function called gameReset().
There are only 10 types of people in the world.
Those who understand binary, and those who don't.