Audit cols(1)

1) Refactor manpage.
2) De-globalize local values.
3) update usage().
4) sort local variable declarations.
5) fix wrong argument in strtonum (3 -> 1).
6) argc-argv style, boolean style.
7) check bytes > 0 before accessing b.lines[i][bytes - 1]
   relying on len only makes sense but let's not push it.
7) don't break on maxlen > (chars - 1) / 2. This didn't even
   make sense.
8) _correctly_ calculate cols and rows in a readable way.
9) Rewrite loop over rows and cols in a readable way and
   using putchar in a loop instead of printf-magic or fputs
   where not necessary.

README

@@ -18,7 +18,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*| chroot          non-posix                    none
 =*  cksum           yes                          none
 =*  cmp             yes                          none
-#*  cols            non-posix                    none
+#*| cols            non-posix                    none
     col             yes                          none
 =*  comm            yes                          none
 =*| cp              yes                          none (-i)