subroutine ''nint'' (version 4)  a.rasinski, dec.1964 (rev. 1024-68)
revised july 1965.  branch for fn added oct 67, nov 69.
revised sept 1969   variable tabular interval (itype=0)
revised dec  1979   step-size control   rdr/kcl

ngo=1 planet-asteroid integration (obsolete)
ngo=2 moon integration (obsolete)
ngo=3 satellite-probe integration (numint called by planet)
ngo=4 n-body integration (numint called by planet)
ngo=5 earth rotation integration
ngo=6 moon rotation integration (obsolete)
ngo=7 planet rotation integration
ngo=8 moon orbit and rotation integration

l1
-1  first step of continuing procedure
0  starting procedure
1  continuing procedure

k1      count of steps -- not used?
k2      count of steps -- used to find end of
starting procedure at k2=19 in eval
and used to control accuracy tests
l4      if .lt. 0 step size not to be changed
used to prevent frequent step size changes
l5      used in tabular output mode
-1 do not change step size
set to -1 in tabular output mode except
for first step after each tabular point.
this prevents the need for a fractional
step to get to the next tabular point.
n1, n2  range of equation number for integration.
first (1 to m), second(m+1 to n).
istp       0  do not use stpctl
-1  make transition to stpctl
1  use stpctl