[daip] XINC in PRTUV

[Gustaaf van Moorsel]

I find confusing behavior when using XINC in PRTUV.  I am selecting
only baseline 13 - 16 using CPARM(9) = 1316.  The first visibility
with that baseline is #43.

o XINC=1 lists visibilities #43, 268, 693, 1018, 1343, 1668, 1993,
   as expected
o XINC=2 lists visibilities #43, 693, 1343, as expected
o XINC=3 lists visibilities #43, 1018, 1993, as expected
o XINC=4 lists visibilities #693, 1993, etc.  Why not start with #43?
o XINC=5 starts with #157666 !
o XINC=6 lists visibilities #43, 1993, as expected
o XINC=20 does not list any visibilities at all, whereas XINC=19 and
   XINC=21 do (of which only the latter starts with #43)

If needed I'll be happy to make the data available.

Gustaaf