* gfortran.h (gfc_is_intrinsic_typename): Add declaration.
* symbol.c (gfc_is_intrinsic_typename): New function.
* parse.c (decode_statement): Check for space in ABSTRACT INTERFACE.
(parse_interface): Use gfc_is_intrinsic_typename.
* decl.c (gfc_match_derived_decl): Ditto.
* module.c (gfc_match_use): Use gcc_unreachable() for
INTERFACE_ABSTRACT in switch().