Correct the Illegal External References

Compiled successfully with Opencpn 3.3.1117, however this plug in
currently works only with Climatology grib files, not Grib-pi. We do not
know why, but perhaps additional changes to Grib_pi or the main program
have been made, causing this new bug to appear.   Thanks to Mike
[Rasbats] and ChuckSK for their help.  Solutions are welcome.