test - experiment : adjustment.cs_32x32x1 (.nlfs)

purpose: 
test the non-linear free-surface in a simple barotropic adjustment
problem.

this experiment is identical to "adjustment.cs_32x32x1",
except:
* use NonLin-FreeSurf  
  (CPP_OPTION.h : "#define NONLIN_FRSURF" and nonlinFreeSurf=3 in data)
* use a Cranck-Nickelson time stepping (implicSurfPress=implicDiv2DFlow=1/2)
  to compute the free-surface pressure anomaly.
* use a smaller time step for a better resolution of gravity waves and
  a larger initial surface pressure anomaly (100.mb) to increase the
  non-linear effects.