Don't prefetch END_FLAG on first print
Don't prefetch END_FLAG on first print

The logic of the prefetch evaluator is such that the END_FLAG is read
as soon as possible, and that Do_Core is never called with END_FLAG
preloaded.  New print logic for a single value case was using END_FLAG
where it should have been using 0, leading to a 0 < END_FLAG comparison.

The comparison was harmless in this case, but similar problems of
understanding lead to incorrect behavior.

Caught by C++ build

draegtun/ren-c,hostilefork/rebol,rgchris/ren-c,hostilefork/rebol,kealist/ren-c,hostilefork/rebol,draegtun/ren-c,draegtun/ren-c,giuliolunati/ren-c,hostilefork/rebol,rgchris/ren-c,kealist/ren-c,draegtun/ren-c,codebybrett/ren-c,kealist/ren-c,kealist/ren-c,draegtun/ren-c,rgchris/ren-c,codebybrett/ren-c,kealist/ren-c,giuliolunati/ren-c,codebybrett/ren-c,codebybrett/ren-c,giuliolunati/ren-c,codebybrett/ren-c,hostilefork/rebol,kealist/ren-c,draegtun/ren-c,hostilefork/rebol,giuliolunati/ren-c,rgchris/ren-c,rgchris/ren-c,codebybrett/ren-c,giuliolunati/ren-c