hdf5_ep

[svn-r21912] Issue 7756 - Creating a dataset in a read-only file caused seg fault when the file is closed.  I fixed the problem by putting a condition check early in H5O_create of H5O.c.  The old code checked it too late, not until a file space is created.  I added a test case in tfile.c to check the creation of group, dataset, attribute, and datatype.

Tested on jam - I've tested the same changes in the trunk with h5committest.