mouse samples.  (Actually don't believe delta-t smaller than .15 sec.)

inside #ifdef brackets.

all those maintained by specks_timespecksptr.  We no longer guarantee
that st->curtime is always in range 0..st->ntimes-1, so just yield NULL
for out-of-range references.  New CURDATATIME(fieldname) does it.

Only call parti_parse_args() if non-CAVE.

"spi fast" -> SPI_PF_AUTO.

toggle-button colors to change.  Lets us (barely) see when
inertia and hrdiagram toggles are selected.

Add new per-particle field, "ismember", to show escapees.

"inertia on/off" and "detach [fullscreen]" commands.

Adds a series of "spi XXX" commands.

in detached mode.

and let postdraw return an int.  Keep looping, re-rendering,
until postdraw returns zero.

and into partiview.cc, using new parti_add_commands hook.

Declare getfloats() (from partibrains.c at the moment).

"where" prints more information.

(Some "kira" commands use kira_set(), which already does this.
Just set "changed" for those which don't.)
Impose a max trail gap (delta time).  Break up trails at time-gaps
exceeding this threshold.