Also added ability capability for netCDF-4 to write and read NIL
values for string type attributes and variables, so these can be read
if used in HDF5 files.
Include are additions to CMakeLists files to reflect new tests.
The in-memory files can be made persistent if nc_create is called with
NC_DISKLESS|NC_WRITE flags set. Initial test case also included.
- Modified ncio mechanism to support
multiple ncio packages; this is so we
can have posixio and memio operating
at the same time.
- cleanup up a bunch of lint issues (unused variables, etc).
