The `NC_HAS_MULTIFILTERS` line in `netcdf_meta.h` was not of the correct form -- showed as
```
#define NC_HAS_MULTIFILTERS
```
Instead of the better form:
```
#define NC_HAS_MULTIFILTERS 0 (or 1 if enabled)
```
Primary Fixes:
* Add a whole variable optimization -- used in the rare case that nc_get/put_vara covers the whole of a variable and the variable has a single chunk.
* Fix chunking error when stride causes whole chunks to be skipped.
* Fix some memory leaks
* Add test cases
* Add one performance test to nczarr_test/. This uses the timer utils from unit_test: timer_utils.[ch].
* Move ncdumpchunks utility from ncdump to nczarr_test
Misc. Other Changes:
* Make check for aws libraries conditional on --enable-nczarr-s3
* Remove all but one bm tests from nczarr_test until they are working.
* Remove another dependency on HDF5 from supposedly non-HDF5 specific code; specifically hdf5_log_hdf5.
* Make the BAIL2 macro be hdf5 specific and replace elsewhere with an HDF5 independent equivalent.
* Move hdf5cache.c to libsrc4/nc4cache.c because it is used by nczarr.
* Modify unit_tests so that some of them are run even if using Windows.
* Misc. small bug fixes and refactors and memory leaks.
* Rename some conflicting tests for cmake.
* Attempted to make nc_perf work with cmake and failed.
Re: GH Issue https://github.com/Unidata/netcdf-c/issues/1900
Apparently the clock_gettime() function is not always available.
It is used in unit_test/tst_exhash.c and unit_test/tst_xcache.c.
To solve this, a number of things were changed:
* Move the timing code to a new file unit_tests/timer_utils.[ch]
* Modify the timing code to choose one of several timing methods
depending on availability. The prioritized order is as follows:
1. If Windows, use the QueryPerformanceCounter mechanism else
2. Use clock_gettime if available else
3. Use gettimeofday if available else
4. Use getrusage if available
Note that the resolution of 3 and 4 is less than 1 or 2.
Misc. Other Changes:
* Move the test in CMakeLists.txt that disables unit tests for WIN32 to unit_test/CMakeLists.txt since some unit tests actually work under Visual Studio.
* Fix some of the unit tests to work under visual studio
* Fix problem with using remove() in zmap_nzf.c
* Remove some warning about use of EXTERNL
