cl_parse: Implement 7th mode for cl_nettimesyncboundmode; jitter compensated dynamic...

cl_parse: Implement 7th mode for cl_nettimesyncboundmode; jitter compensated dynamic adjustment rate

This mode aims to prevent network jitter or other disturbances from
	significantly affecting the client's timekeeping,
	by correcting gradually (max 10% of mean error per tic).

The rolling harmonic mean gives large time error outliers low significance.

Correction rate is dynamic, determined by mean error size.
Time is correct within a few tics of connect/map start despite no hard bounding.

The adjustment approach is from mode 5 and can achieve
	microsecond accuracy if client frametime is a multiple of server frametime.

Prevents 0ms move frame times with uncapped fps.

Smoothest mode esp for vsynced clients on servers with aggressive inputtimeout.

Authored by bones_was_here
https://gitlab.com/xonotic/darkplaces/-/merge_requests/112

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@13115 d7cf8633-e32d-0410-b094-e92efae38249