Purpose:
Added missing fortran functions h5set(get)_buffer_f.
Also added docs and tests for them.
Solution:
Currently functions do not accept conversion and background buffers.
This corresponds to H5set(get)_buffer call with buffer pointers
set to NULL. If there is a demand, I can overload the functions
to have new parameters and go through all trouble creating functions
for all supported datatypes.
Platforms tested:
Solaris 2.7, Linux 2.2., IRIX64-6.5
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