meson: improve summary() printout

meson: improve summary() printout

Pass bool_yn kwarg to summary() to make it
print boolean arguments as nice coloured YES/NO
instead of true/false.

We can also pass multiple arguments like a bool
and a disabled_reason string. In meson 0.54 these
can be printed on one line if we set the line_sep
kwarg. In meson 0.53 these will always be printed
on two lines (and it will warn about the line_sep
arg), so only pass two args if docs are disabled
and otherwise just pass one arg, so we don't end
up with an ugly empty line with meson 0.53.