Add in a void function

For aesthetic reasons, some people might prefer to write `return void`
instead of `return ()`.  It's not possible to fetch a void value from
a word, so that has to be a function...which makes it less efficient.
It also could be confusing, because unlike `get 'blank` or `get 'bar`
or `get 'true` the value that comes back would be a function.

But rather than be prescriptive that people have to say () in the source
if they don't like the way that looks, this standardizes the option
so everyone doesn't have to make this function themselves.

Author: hostilefork

src/mezz/base-defs.r

@@ -151,6 +151,13 @@ ok?: func [
 blank: _
 bar: '|
 
+; void is a little bit dodgy because it's not an alias for a value (e.g. you
+; GET it and you'll have a function).  But it cannot be a value retrieved via
+; a word because void isn't a value.  Still, having it as a word might
+; be considered by some to be more literate than `()`.
+
+void: does []
+
 ; Experimental shorthand for ANY-VALUE? test (will also be VALUE?)
 ;
 ?: :any-value?