vtgcm/trunk:
 - Now have VGCM data for 10 zp levels -16 to -11.5 by 0.5 for nudging.
   Modified oxvgcm_lbc/mknc_lbc.pro to read the new *.dat files and
   create oxvgcm_lbc.nc with the added lev dimension. The old ascii
   *.txt files in the oxvgcm_lbc directory are replaced by the *.dat files.
 - Modifications to oxvgcm.F to read the multi-level data in oxvgcm_lbc.nc,
   and to lbc.F, dt.F and duv.F to nudge t,u,v from each zp level.
   (Z still gets only the lower boundary from VGCM)
 - The new multi-level oxvgcm_lbc.nc file was copied to $TGCMDATA/vtgcm 
   at HAO (/hao/aim/tgcm/data/vtgcm) and at CISL (/hao/tgcm/data/vtgcm).