bug#18059: 24.3.92; defvar and special variables

[Drew Adams]

> So does "end of the current lexical scope" make sense?  I think I've
> been looking at this for too long, it's hard for me to tell by now.
> 
>     Likewise, you can tell the compiler that a variable is defined using
>     @code{defvar} with no initial value.  (Note that this marks the
>     variable as special, i.e.@: dynamically bound, but only until the end
>     of the current lexical scope, or file if at top-level.)

 ... but only _within_ the current lexical scope,
 or within the current file if at top-level.

Lexical scope is defined lexically.  It can have two
limits or "ends", but it's best to avoid speaking of
beginning and end, as that can suggest temporal end.

https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node43.html