Merging in latest from upstream (HDFFV/hdf5:refs/heads/develop)

* commit '0772b975d1d2bfa15aedeb4b6e2c2aac78c61a2f':
  Fix missing free in H5T__ref_mem_read()
  Fix bugs in H5VL file comparison code.  Add short circuit success to H5VL_cmp_connector_cls().
  Implement file comparison VOL callback.  Other changes to allow references to work with non-native connectors.  There is a bug somewhere.
  Add support for point selections to H5S_select_project_intersection.
  Remove H5VL_NATIVE_FILE_GET_FILE_ID and add H5VL_OBJECT_GET_FILE
  Revert "Make a squash commit of 'Quiet some warnings by adjusting warnings level and fixing some code.' (commit 5c911d8baf)"
  Revert "Oops, remove more C99 designated initializers for VS 2010 compatibility."
  H5R: fix H5Tconv to check for null references
  Trivial parameter renaming in VOL API calls.
  Move checking for zero offset in selection adjust calls to the selection callbacks.  This makes the procedure for checking it consistent across selection types and between _s and _u, ensures it is always is performed even when called within the H5S package, and removes the redundant check that would occur when callins H5S_select_adjust_s() from outside the H5S package.
  Replace H5Sselect_adjust_u() and H5Shyper_adjust_s() with H5Sselect_adjust.  Implement "adjust_s" callback for all selection types.  Add range checking to H5Sselect_adjust().

tools/lib/h5diff_array.c

@@ -2251,9 +2251,6 @@ static hsize_t character_compare(char *mem1, char *mem2, hsize_t i, size_t u,
  *-------------------------------------------------------------------------
  */
 
-#pragma GCC diagnostic push
-#pragma GCC diagnostic warning "-Wunused-but-set-variable"
-
 static hsize_t character_compare_opt(unsigned char *mem1, unsigned char *mem2,
         hsize_t i, int rank, hsize_t *dims, hsize_t *acc, hsize_t *pos, diff_opt_t *opts, const char *obj1, const char *obj2, int *ph)
 {
@@ -2314,7 +2311,6 @@ static hsize_t character_compare_opt(unsigned char *mem1, unsigned char *mem2,
 
     return nfound;
 }
-#pragma GCC diagnostic pop
 
 /*-------------------------------------------------------------------------
  * Function: diff_float