hdf5_chunking_query_bmr

[svn-r24870] Description:
    - Added another overload for char* argument:
        ssize_t getComment(const char* name, const size_t buf_size, char* comment)
    - Changed default value to 0 for the other two getComment methods
    - Added HDmemset to after every char string allocation to clear the buffer
    - Added a null terminator to the comment returned from the C call, in
        getComment methods
    - Some minor cleanup
    Merged from trunk: -r24865 -r24867
Platforms tested:
    Linux/ppc64 (ostrich)
    Linux/32 2.6 (jam)
    SunOS 5.11 (emu)