Problem: 'findfunc' can't return extra info for cmdline completion
(Maxim Kim).
Solution: Handle 'findfunc' return value in cmdline completion like that
of "customlist" functions (zeertzjq).
fixes: #20155closes: #20158
Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>