Generate Doxygen XML output for ".h" files
Generate Doxygen XML output for ".h" files

Add ".h" to the list of file extensions that are detected by Sphinx which in
turn calls Doxygen to generate the documentation.  This is needed to document
the C API on ReadTheDocs.

Rombur/DataTransferKit,ORNL-CEES/DataTransferKit,Rombur/DataTransferKit,ORNL-CEES/DataTransferKit,Rombur/DataTransferKit,dalg24/DataTransferKit,ORNL-CEES/DataTransferKit,Rombur/DataTransferKit,dalg24/DataTransferKit,dalg24/DataTransferKit,dalg24/DataTransferKit,ORNL-CEES/DataTransferKit