hdf5_ep

[svn-r22156] Issue 7785 - Writing or reading many small chunks ran out of memory and caused seg fault. I added checks in two places to make sure the library returns error stack 
when it fails to allocate memory.  I didn't add any test to the test suite since there is no good way to test it.  But I tested and verified the error stack by hand.

Tested on jam - this is a merge from the trunk.