hdf5_ep

[svn-r27744] Merge of r27728 from trunk.

Added -qflag=w:w to config/ibm-flags. This will suppress informational
messages on AIX, suppressing thousands of "__attribute__ is non-portable"
messages in the AIX nightly test output.

Tested on: Nothing. I have no access to an AIX machine. This change
suppressed the informational warnings on last night's AIX run, however.