hdf5_ep

[svn-r16608] Bug fix (#1161): When a family file created with v1.6 library is opened and closed with 
v1.8 library, v1.8 library writes the driver info block in the superblock.  But v1.6
doesn't write it.  This caused the data after the superblock to be overwritten.  The
solution is to use a flag to indicate when the original file doesn't have the driver
info, v1.8 library doesn't write it either.

Tested on jam.  I have some trouble to access smirom and linew using h5committest.