h4h5tools

Purpose:
    Bug fix and code cleanup
Description:
    IRIX (modi4) was picking up wring strdup function causing compilation to fail
    on modi4. hdf.h was included in the h5toh4.h header file  along with mfhdf.h
Solution:
    Replaced strdup with HDstrdup, and removed hdf.h from the h5toh4.h header file
Platforms tested:
    modi4 (64), eirene, arabica (32)