hdf5_msb

[svn-r18618] Description:
        Add new internal object header routines to query the header chunk that
a message is in, and to lock/unlock a message into a chunk (so it doesn't get
moved into another chunk during allocation/free events).

        Also, move dataspace message to beginning of object header messages
added to a dataset's object header, so it can be locked into chunk #0 (when
performing SWMR operations).

Tested on:
        FreeBSD/32 6.3 (duty) in debug mode
        FreeBSD/64 6.3 (liberty) w/C++ & FORTRAN, in debug mode
        Linux/32 2.6 (jam) w/PGI compilers, w/default API=1.8.x,
                w/C++ & FORTRAN, w/threadsafe, in debug mode
        Linux/64-amd64 2.6 (amani) w/Intel compilers, w/default API=1.6.x,
                w/C++ & FORTRAN, in production mode
        Solaris/32 2.10 (linew) w/deprecated symbols disabled, w/C++ & FORTRAN,
                w/szip filter, in production mode
        Linux/64-ia64 2.6 (cobalt) w/Intel compilers, w/C++ & FORTRAN,
                in production mode
        Linux/64-ia64 2.4 (tg-login3) w/parallel, w/FORTRAN, in debug mode
        Linux/64-amd64 2.6 (abe) w/parallel, w/FORTRAN, in production mode
        Mac OS X/32 10.6.3 (amazon) in debug mode
        Mac OS X/32 10.6.3 (amazon) w/C++ & FORTRAN, w/threadsafe,
                in production mode