+Add the runtime parameter VERTEX_SHEAR_OBC_BUG

  Added the new runtime option VERTEX_SHEAR_OBC_BUG that can be set to false to
use masks to set the thicknesses interpolated to velocity points when open
boundary conditions might be used.  This commit includes the addition of
checksums of the input stratification and shear squared when DEBUG is true.  It
also refactors the code setting the output diffusivity in
Calc_kappa_shear_vertex to move some logical branches outside of the do loops
for efficiency.  A number of spelling errors were corrected, and some
vertex-point indices were converted to uppercase to follow the MOM6 soft
convention in MOM_kappa_shear.F90.  By default, all answers are bitwise
identical, but there is a new runtime parameter.

Author: Hallberg-NOAA