remove unnecessary variable and rename some #3

In main.cpp, the findAloneWindow() function:

The variable "mapped" is not used, I'd like to get rid of It.

I'd like to rename the parameters "r" and "p" to something a bit more meaningful, for instance:

r --> root_id

p --> parent_id

Some doc about the XQueryTree function:
https://tronche.com/gui/x/xlib/window-information/XQueryTree.html

Sounds good to me. Actually for this kind of small changes, feel free to prepare the code and PR directly 😉

If It would have been about the removal of the variable only, I wouldn't ask ; but I had to know if you were willing to rename things here and there, therefore I snapped the occasion up.

Resolved by PR #5