Merging in latest from upstream (HDFFV/hdf5:refs/heads/develop)
* commit 'd3ef866a2963ce93d0b95184534a70849b6fa11d':
Revise API for H5get_alloc_stats() to take a struct instead of separate values.
Move the GNU warnings configuration under config/gnu-warnings/ and trim the filename prefixes. Update config/gnu-flags to suit.
Fixed the RELEASE.txt note for HDFFV-11057
Fix shutdown errors when using the HDF5_VOL_CONNECTOR environment variable to set a dynamically loaded plugin as the default VOL connector. Fixes HDFFV-11057
Fix threadsafe for new test
Fix issues when deserializing point/all/none selection with version beyond the library's supported version: (1) Verify the decoded version before proceeding further with deserialization (2) Close the dataspace if errors occurred after opening the dataspace
Very minor comment change in H5VLconnector.h.
Add routines to query the library's free list sizes and allocation stats.
By default, demote warnings promoted to errors back to warnings.
Incorporate the H5_ECFLAGS into the library CFLAGS. Now a bunch of errors will occur. Next commit will demote the warnings promoted to errors back to warnings again.
Break out warnings into more files that autoconf and CMake can share. This change temporarily disables the warnings that were promoted to errors, but I will add those warnings back as warnings, not errors, in the next commit.
Avoid a crash, don't check if we're flushing when the file is closing: there's no need to check if the metadata cache is flushing if we already know the file is closing, because the condition we rely on is "closing OR flushing." Further, the cache may have already gone away, so sometimes calling into the cache to see if it's flushing will crash the program.
