`disp.width` calcs with width changing styles

[brodieG]

Notice how disp.width does not help in the least avoid wrapping:

> my.pal <- PaletteOfStyles()
> my.style <- StyleRaw()   # See `?Style` for custom styles
> my.style@[email protected] <- function(x) sprintf("--%s--", x)
> my.pal["ansi256", "light", "rgb"] <- list(my.style) # note `list()`
> ## Output has no format now for format/color.mode/brightness
> ## we modified ...
> ## `pager="off"` for CRAN compliance; you may omit in normal use
> diffPrint(
+    1:3, 2:5, format="ansi256", color.mode="rgb", brightness="light",
+    palette.of.styles=my.pal, pager="off", disp.width=80
+ )
< --1:3--      > 2:5        
@@ 1 @@        @@ 1 @@      
< [1] --1-- 2  > [1] 2 3 4 5
:  3           ~            

[brodieG]

This is not trivial, and not very valuable. Mostly we need to re-order code in as.character so we can get the true width of the output. This is likely to be somewhat complicated to do properly without breaking other stuff.

For now we just documented this problem.