hdf5_ep

[svn-r8721] Purpose:  Bug fix and test.

Description:  Function H5Gget_objtype_by_idx failed to handle soft link
object.  The library returned object type by calling H5G_get_type through
H5B_iterate.  But H5G_get_type only deals with objects with valid header address
which soft link doesn't have.

Solution:  In H5G_node_type, make soft link a special case by checking if
the object type is H5G_CACHED_SLINK.  Also added a test of soft and hard links
to titerate.c

Platforms tested:  h5committest and RH 8(fuss).