hdf5_msb

[svn-r24098] Issue 8500 - H5detect.c has trouble to find info for long double with GCC 4.8.  A user in the forum found the
problem in H5detect.c (uninitialized buffer) and provided the solution.  I checked it in yesterday.  But it 
turned out to be a false fix.  So I'm back it out.

Tested on jam - reverse of changes.