Initialize unset fields for GC sake in APPLY
Initialize unset fields for GC sake in APPLY

When a call frame is linked in and has been marked CALL_MODE_ARGS or
CALL_MODE_FUNCTION, more fields in that frame are expected to be valid
than at CALL_MODE_GUARD_ARRAY_ONLY.  Aggressive GC caused by reverting
to the buggy GC watermark after committing the APPLY change picked up
that two fields were missing from the initialization.

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