(read_key_sequence): Use flags instead of gotos to

(read_key_sequence): Use flags instead of gotos to
enable the Microsoft C compiler to compile the routine.

(read_avail_input) [WINDOWSNT]: Just return 0.

(make_lispy_event): Record double and triple for drags.
Put in click_modifier for multi-clicks.
(read_key_sequence): Convert double-drag first to plan drag,
and only later try a click.