Split y instruction into seperate file
Starting refactoring y
Complete refactoring of the y instruction
Seperate functions are defined for each section of info to push. When
the argument to y is non-positive, they are all called, and then the
results pushed in sequence. When the result it positive, they are called
in sequence, and as soon as the required cell number has been hit, that
cell is pushed and the rest of the functions aren't called. Still
doesn't quite work for picking data off that was previously on the
stack. Probably an off-by-one error or something