bug fixes for obs_seq_to_netcdf and grabbufr.x
Bug fixes:
- Added logic to obs_seq_to_netcdf to keep track of whether a files has been created for an epoch during that run of obs_seq_to_netcdf. Previously if there were multiple obs_sequence files in an epoch, the epoch file was being created afresh for each obs_seq file. Thus, only obs from the last file in the list were present in obs_epoch.nc
- The PGI compiler requires a declaration for the STAT function. This prevents STAT exiting with an error when using long filenames.