[Support #GVL-886634]: Unidata Synopdata decoders

Stefan,

the problem is that all the perl decoders are designed to work only in real
time because the date information doesn't contain year and month. i added
an -i option to permit decoding of older files. ie.

syn2nc -i syn.cdl data 200605 < 06050100_syn.wmoi 


attached in a new syn2nc decoder

robb...