hyc2ave : 
   Routine creates a file containing mean values of the variables contained 
   in the input files. All input files must be of the same type.  Note that 
   the means of layer (3D ocean) variables are weighted by layer thickness.
   Usage:
      hycave filetype file1 file2 file3 ....

   filetype argument is either restart, nersc_daily, nersc_weekly, or archv
   Example:
      hycave nersc_daily TP3DAILY_1990_240_1990_313.a TP3DAILY_1990_240_1990_314.a 

   Files are dumped to files where year=9999, day=999, hour=99. For weekly average 
   week=99 and day of week=9.

   Routine requires the regional.grid and regional.depth files to be present.
   Routine supports restart, nersc_weekly, nersc_daily and archv file types.

   Routine uses the library routines in libhycnersc.a

Knut Liseter, 23. November 2008