hdf5_msb

[svn-r6223] Purpose:
    Bug fix - informed by Kent

Description:
    Some identifiers were flagged as unresolved symbols when building
    with c++ on Windows.  The reason is the name of these identifiers
    were changed by the c++ compiler, also called name mangling.

Solution:
    Moved
        #ifdef __cplusplus
        extern "C" {
        #endif
    to include the offending identifiers so the c++ compiler will take
    them as is.

Platforms:
    SunOS 5.7 (arabica)
    Linux 6.2 (eirene)
    Windows 2000