The predicate for bmp-char objects.
bmp-char-p object => result
A Lisp object.
t if its argument is a character with a code less than
#x10000, otherwise it returns
bmp-char-p was new in LispWorks 7.0. In LispWorks 6.1 and earlier versions
simple-char-p has the most similar meaning.
LispWorks User Guide and Reference Manual - 20 Sep 2017