The current ncgen does not properly handle very large
data sections. Apparently this is very uncommon because
it was only discovered in testing the new zarr code.
The fix required a new approach to processing data sections.
Unfortunately, the resulting ncgen is slower than before
but at least it is, I think, now correct.
The added test cases are in libnczarr, and so will
not show up until that is incorporated into master.
Note also that fortran code generation changed, but
has not been tested here.
Misc. Changes
1. Cleanup error handling in ncgen -lc and -lb output
2. Cleanup Makefiles for ncgen to remove unused code
3. Added a program, ncgen/ncdumpchunks, to print
the data for a .nc file on a per-chunk format.
4. Made the XGetOpt change in PR https://github.com/Unidata/netcdf-c/pull/1694
for ncdump/ncvalidator
