gradsver() - get/compare GrADS version.
ret = gradsver( [cmpver] )
This script function is beta release, because function of comparison is not perfectly implemented.
- GrADS version to be compared with the current GrADS.
- GrADS version if cmpver is not specified. =1 if current GrADS is newer than cmpver, =0 if equivalent, =-1 else.
- gradsver.gsf (necessary)