hdf5_ep

[svn-r21557] Port r21556 to 1.8 branch

Purpose: Fix bug in H5Ocopy

Description:
H5Ocopy could get confused when copying a named datatype containing an
attribute which used that named datatype as its datatype.  This happened
because H5Ocopy would recurse into the attribute's datatype before the object
the attribute was in was fully copied (i.e. before the "post-copy" pass).
Modified H5Ocopy to avoid recursing before the post-copy step in this case.
Required many changes, including to how non-committed shared messages are
copied.

Tested: jam, koala, heiwa (h5committest); durandal