Merge pull request #781 in HDFFV/hdf5 from ~NFORTNE2/hdf5_naf:hdf5_1_10 to hdf5_1_10
* commit '837dc4bb51e3d3e823235228a33f6ffeae166b52':
Add RELEASE.txt note for HDFFV-10274. (cherry picked from commit f7a7d0a00613cba997212fa8032091629a678797)
Initialize hid_t variables in test_Attr_bug9.
Fix HDFFV-10274. When deleting all (or almost all) of the messages in an object header chunk, where the total amount deleted was greater than 64K, an error would occur due to an off by one error in the code that handled that case. Fixed this and added a test case.
