input. For now, only the tracer innitial conditions can be set by
  using, for example,

  ictracer_grd_layers=2
  ictracer_grd_file="tmask.grd"


  for this to work, the ggrd libraries from HC, as well as the -lgmt 
  and -lnetcdf need to be linked, and -DUSE_GGRD needs to be defined
  on compile time.

- rewrote TDEPV viscosity options 3 and 4 slightly to make them more
  efficient

- added TDEPV viscosity option 6 

		 eta = N_0 exp(E(T_0-T) + (1-z) Z_0 )

- took layers subroutine in Construct_arrays.c apart to allow calling
  the same function in a more flexible from other subroutines

- addded error handling routine "myerror" to Pan_problem_misc_functions

- made the output behavior of the multigrid solver convergence
  parameters consisent with verbosity setting (ie. use report instead
  of always stderr output)

- changed tracer input parameter "tracer" and "chemical_buoyancy" to
   boolean routine for added flexibility (I hope)

- made check_initial_composition consistent with tracer advection,
      exits after warning only for E->trace.itracer_warnings==1

- debugging output in Full_tracer_advection.c and Tracer_setup only
  gets printed to file for E->control.verbose == 1

- fixed some typos in Output_gzdir (that might have been introduced by
  asynchronous svn updating or something like that)