hdf5_ep

[svn-r7494] Purpose:
    Bug fix

Description:
    Buffer for decoding superblock's driver information was too small when
using some VFDs (like the multi-file VFD).

    Also made FPH5 code more portable and obvious when it's broadcasting the
superblock from the captain process to the other clients.

Solution:
    Allocate the buffer for the driver information dynamicly

Platforms tested:
    Copper
    No h5committest because it's already working on other platforms.