immediate ansi 15.6.2.2532
<TOOLS>
check the condition in the CS-STACK. If true let the following
text flow into INTERPRET , otherwise eat up everything upto
and including the next [ELSE] or [THEN] . In case of
skipping, count nested [IF] ... [THEN] constructs.
this word provides a simple pre-compiler mechanism
reference: p4_bracket_if in ../src/toolkit.c:0354, export CI [IF]