It seemed like a good thing at first to combine all the movement stuff
in a single function, however as soon as you want to move multiple lines
at once it becomes very difficult to do that, especially if you aren't
familiar with C.
This commit splits it into 4 separate functions, where the argument
(arg->i) is how many times we move. This means it is now possible to
choose how many lines to move without even editing the function itself,
just through keybinds. This also makes the "fastmove" keybindings
redundant.
Note that calcoffsets() and drawmenu() after that must be called AFTER the for loop added with this commit, otherwise
you can see the selection moving from each line to the next which is
rather ugly.
