Since we are adding Xrandr support to allow for automatic dpi detection,
split screen handling code into a new file as part of the effort to
simplify x.c
x.c has grown into an unmaintainable blob. Moving it in its own
subdirectory is the first step to splitting it into submodules each of
which will have a well defined job so that a lot of the code can be
abstracted to improve readability and make it much easier to maintain.
This process will be done one small part at a time only when we need to
change significantly change a part of the file, there is no need to
break what already works.
