Update outdated comment on COMBINATOR

The need to change the usermode version meant the native combinator code was
dropped.  They should be updated in sync, in the same file (where the user
code is in a comment in a C file that is scraped out by the build process).

src/mezz/uparse.r

@@ -87,12 +87,12 @@ Rebol [
 ; A special COMBINATOR generator is used.  This saves on repetition of
 ; parameters and also lets the engine get its hooks into the execution of
 ; parsers...for instance to diagnose the furthest point the parsing reached.
-
+;
 ; !!! COMBINATOR is used so heavily that having it be usermode makes UPARSE
-; prohibitively slow.  So it was made native.  However the usermode version is
-; kept as a proof of concept that a user *could* have made such a thing.  It
-; should be swapped in occasionally in the tests to overwrite the native
-; version just to keep tabs on it.
+; prohibitively slow.  The ultimate goal is to have native and usermode
+; implementations both exist, with the usermode version being swappable in as
+; proof of concept that nothing is being done by the native that the user
+; could not have done...just more slowly.
 ;
 ; We would like it to be possible to write an "easy" combinator that does not
 ; do piping of the pending elements, but takes it for granted as coming from