gcc/c/c-parser.c b/gcc/c/c-parser.c

         - Add handling of use_device clause in c_parser_omp_clause_name().
         - Add new function c_parser_oacc_clause_use_device() to handle
           use_device clause with host_data.
         - Add handling of use_device clause in c_parser_oacc_all_clauses().
         - Add new macro OACC_HOST_DATA_CLAUSE_MASK.
         - Add new function c_parser_oacc_host_data() to handle host_data.
         - Add handling of host_data pragma to c_parser_omp_construct().

     gcc/c/c-tree.h b/gcc/c/c-tree.h

         - Add definition for c_finish_oacc_host_data().

     gcc/c/c-typeck.c b/gcc/c/c-typeck.c

         - Add new function c_finish_oacc_host_data().