Make `speedup_frame_skip` and `speedup_throttle` independent settings,
with `speedup_frame_skip == 0` when `speedup_throttle` is not in effect,
and `speedup_throttle == 100` when `speedup_frame_skip` is in effect.
This fixes a previously introduced bug where `speedup == true &&
speedup_frame_skip = X` was never enabled.
This also allows `speedup_throttle == 0` for no throttle and no frame
skip during speedup.
Also set the upper bound on `throttle` and `speedup_throttle` to `450`
instead of `600`, as the DirectSound driver does not support values
higher than that.
In the DirectSound implementation of `setThrottle`, for `throttle == 0`
use a `throttle == 450` frequency multiplier, because a zero frequency
does nothing.
- Fix#719.
Signed-off-by: Rafael Kitover <rkitover@gmail.com>
c169420fbc