hdf5_ep

[svn-r26398] Merges r26333 from trunk

Eliminates gcc warnings due to -Wunsuffixed-float-constants.

- Adds 'F' suffixes for most float constants.

- A few constants MUST be of type double. These now receive the long
  double L suffix and are then cast to double. I do this via a new
  H5_DOUBLE() macro which was added to H5private.h.

- Additionally, some 1.8-specific float suffixes were added.

Fixes: HDFFV-9148

Tested on: h5committest