patch 9.0.2169: Vim9: builtin funcs may accept a non-value

patch 9.0.2169: Vim9: builtin funcs may accept a non-value

Problem:  Vim9: builtin funcs may accept a non-value
Solution: Restrict builtin functions that accept `type`

This PR finishes off detection and prevention of using a type as a
value. It takes care of builtin functions. However there are some
builtin functions, that need to be able to handle types as well as
non-args: instanceof(), type(), typename(), string().

A "bit", FE_X, is added to funcentry_T; when set, the builtin function
can handle a type (class or type-alias) in addition to a value.

Noteworthy change: Discovered that in compile_call() the builtin add()
is compiled inline instead of calling the builtin. Had to add a check
there.

closes: #13688

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>