MakeSelectionVisible in window.c was not paying attention to wrapped lines. To

MakeSelectionVisible in window.c was not paying attention to wrapped lines.  To
see the problem in an older version:

1.  Open a large file and scroll to the center somewhere
2.  Enable continuous wrapping and resize window so lots of lines wrap
3.  Select a word and make a mark with Alt+M,a
4.  Page Up or Down for several screens
5.  Go to the mark with Alt+G,a

If there are enough wrapped lines between your position and the mark then the
selection and the cursor will be completely offscreen.

Also restructured the function so that horizontal scrolling is not bypassed
prematurely.