Search and replace all instances of unsigned with size_t.
-- Test by compiling under Linux 64, Win32, and Win64.
-- Win64 found the most errors because their "size_t" is not a "long".
-- Required modifying NetCDF-3 C++ interface to resolve issues on Win66.
Fix errors in unsigned math for az-1.
Merge branch 'unsigned2size_t' of https://github.com/campreilly/UnderSeaModelingLibrary into unsigned2size_t