PR c++/24009
	* input.h (restore_input_file_stack): Declare.
	(INPUT_FILE_STACK_BITS): Define.
	* toplev.c (fs_p, input_file_stack_history,
	input_file_stack_restored, restore_input_file_stack): New.
	(push_srcloc, pop_srcloc): Check for input_file_stack_tick
	overflowing INPUT_FILE_STACK_BITS bits.  Save new state of stack.
	(pop_srcloc): Don't free old state of stack.

cp:
	* parser.c (struct cp_token): Add input_file_stack_index.
	(eof_token): Update.
	(cp_lexer_get_preprocessor_token): Save input_file_stack_tick.
	(cp_lexer_set_source_position_from_token): Restore input file
	stack.

From-SVN: r116479