* gengtype.c (new_structure): Return the structure.
(create_option): Add an extra "next" argument.
(create_field): New function.
(adjust_field_rtx_def): Use create_option and create_field.
Remove a now-unnecessary call to find_structure.
(adjust_field_tree_def): Likewise.
(note_yacc_type): Remove an unnecessary call to find_structure.
* gengtype.h (new_structure): Return the structure.
(create_option): Add an extra argument.
* gengtype-yacc.y (type): Remove unnecessary calls to find_structure.
(option): Adjust calls to create_option.