m.e.ash   march 1967    subroutine plrd1
reference to s-body tape added 1977 jul - j.f.chandler
first five records of planet tape are read
also set up planet shape quantities

decide if psi0,i0 or alpha0,delta0 needs to be calculated.
this was done in bodred, but needs to be done again if
iterating and changing parameter values.  warning -- if i0
and psi0 are being adjusted, new r.a. and dec. will be
calculated.  this means that you cannot iterate if adjusting
i0,psi0 simultaneously with r.a. and dec.