This change-set modifies PR https://github.com/Unidata/netcdf-c/pull/2555
to add the changes listed below. Most of these changes are required
by changes to the Java remotetest.unidata.ucar.edu server.
## DAP4 Related Changes
* Add tests *dap4_test/test_constraints.sh* and *dap4_test/test_hyrax.sh*.
* Provide explicit list of remotetest files to test.
* Cleanup local checksum computing and verification.
* Define a temporary Hyrax hack flag to deal with the way Hyrax handles checksums and add "#hyrax" fragment flag for it.
* Add a hack to get past an LGTM problem with using "http:".
* Improve debug support.
## Other Changes
* Cleanup the recipe in *docs/nczarr.md* for building *aws-sdk-cpp* library.
re: https://github.com/Unidata/netcdf-c/issues/1451
The situation with the various DAP (and other) remote test
servers is currently in a state of flux. For example, Unidata
admin is planning to forcibly shift the remote test server to
remotetest.unidata.ucar.edu soon. In addition, the server
test.opendap.org has shown some recent instability.
The result is that various DAP (and byterange) tests can fail
unexpectedly. This is an irritant to users and reveals nothing
about test sucess or failure.
Solve by modifying tests to report server inaccessibility and
otherwise pretend to succeed.
This puts an onus on Unidata to detect such server failures, but
will not cause users to see spurious failures. [Note. Do similar
fix for netcdf-java]. The check is:
1. export SETX=1 to cause all the shell scripts to trace
2. search the log files for the phrase "WARNING" (in upper case)
and see if it is complaining about not finding a server.
Misc. Changes
-------------
1. Added a pingurl program to see if a server was up.
2. modified some test case url targets
