subr. prdobs - j.f.chandler - 1983 feb
read obslibs and iobcon for nrmict and prdict.
handle logic for input (and output) tapes, overriding errors,
and data editing.

nrmprd= code for the caller: 1-nrmict, 2-prdict
itype = type of record desired:
1-get next tape and read the type 1 and type 2 records
(iabs1=0 if none)
2-(no effect)
3-read the type 3 record, set up pointers and match iobcon,
(ncodf=0 if none)
4-read type 4 record and set error weights (ncode=0 if none)