Deal with the three classes of variables...

1) ` vars which are always expanded.
2) & vars which are expanded "sometimes" (generally for display stuff).
3) "pure" vars which are only expanded when they are the entire string.

The main change here is in the & var handling... lw() no longer
expands these, so they can be displayed to the user... they are now
expanded in the following cases:

1) Anything that calculates the displayed length.  The assumption
   here is that the string will be passed to one of the following
   things.
2) Bar updates, either @quebar or @saybar
3) @do addlog
4) @do write
5) @moremap
6) @progname
7) @show
8) @writefile