PR preprocessor/69177 and PR c++/68819: libcpp fallbacks and -Wmisleading-indentation

PR preprocessor/69177 and PR c++/68819: libcpp fallbacks and -Wmisleading-indentation

gcc/c-family/ChangeLog:
	PR c++/68819
	* c-indentation.c (get_visual_column): Add location_t param.
	Handle the column number being zero by effectively disabling the
	warning, with an "inform".
	(should_warn_for_misleading_indentation): Add location_t argument
	for all uses of get_visual_column.

gcc/testsuite/ChangeLog:
	PR c++/68819
	PR preprocessor/69177
	* gcc.dg/plugin/location-overflow-test-1.c: New test case.
	* gcc.dg/plugin/location-overflow-test-2.c: New test case.
	* gcc.dg/plugin/location_overflow_plugin.c: New test plugin.
	* gcc.dg/plugin/plugin.exp (plugin_test_list): Add the above.

libcpp/ChangeLog:
	PR preprocessor/69177
	* line-map.c (LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES): New
	constant.
	(LINE_MAP_MAX_LOCATION_WITH_COLS): Add note about unit tests
	to comment.
	(can_be_stored_compactly_p): Reduce threshold from
	LINE_MAP_MAX_LOCATION_WITH_COLS to
	LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES.
	(get_combined_adhoc_loc): Likewise.
	(get_range_from_loc): Likewise.
	(linemap_line_start): Ensure that a new ordinary map is created
	when transitioning from range-packing being enabled to disabled,
	at the LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES threshold.  Set
	range_bits to 0 for new ordinary maps when beyond this limit.
	Prevent the "increase the column bits of a freshly created map"
	optimization if the range bits has reduced.

From-SVN: r232379