Make sure pp_spi_init() is exported where plugins.c can see it.

whether we have a patched FLTK.

but only if FL_STEREO is defined.
Otherwise use old GLX/Unix-specific way.

and refer specifically to Marcus Thiebaux's virdir
since there's now also a Matt Hall version.

check for libfltk_gl.a and .so.  Can't (?) use AC_CHECK_LIB
since it only has C++ entry points.

now moved into partimenu.c.

31 (or maybe 32).

"rawdata -a" particle-dump includes position, color, brightness too.

Allow more subcams.

dvmmul -- don't use entry [3] of a 3-component point!

for performance etc. tests.

And, in partiview version, make sure to *use* o2d/d2o if provided!