* cppfiles.c (struct _cpp_file): Rename once_only_next to
next_file. Remove import and pragma_once, add once_only.
(find_file): Add new file structures to the all_files list.
(should_stack_file): Mark #import-ed files once-only, and
don't stack them if the file has already been stacked.
(_cp_mark_file_once_only): Simplify.
* cpphash.h (struct cpp_reader): Rename once_only_files
to all_files. Rename saw_pragma_once to seen_once_only.
(_cpp_mark_file_once_only): Update prototype.
* cpplib.c (do_pragma_once): Update.
testsuite:
* import1.c, import2.c: New tests.
From-SVN: r70106
