hdf5_chunking_query_bmr

[svn-r24087] Rename the private H5RC (reference count) module to H5UC (Use Count).
This is needed to avoid a conflict with the Read Context object to be
introduced in another Project.

No impact on users, since this is a private module, and low for
developers as the RC module use is very sparse in the library.

Tested with h5committest.