PR preprocessor/69664: fix rich_location::override_column

gcc/testsuite/ChangeLog:
	PR preprocessor/69664
	* gcc.dg/cpp/trad/comment-2.c: Add expected column number.
	* gcc.dg/cpp/warn-comments.c: Likewise.

libcpp/ChangeLog:
	PR preprocessor/69664
	* errors.c (cpp_diagnostic_with_line): Only call
	rich_location::override_column if the column is non-zero.
	* line-map.c (rich_location::override_column): Update columns
	within m_ranges[0].  Add assertions to verify that doing so is
	sane.

From-SVN: r233223