Commits
Merge pull request #2367 in HDFFV/hdf5 from ~DYOUNG/werror:unused to develop * commit '50aac126d7c4082c2aeb0f3a68cad26bd1cd9783': Start to document the function/parameter/variable attribute macros. Filter all of the new _USED / _UNUSED type modifiers. H5_HAVE_PARALLEL, _DEBUG_API, etc. Add attributes to some variables and parameters that are unused under some configurations.