[Diagnostic Patch] don't print column zero

[Diagnostic Patch] don't print column zero

https://gcc.gnu.org/ml/gcc-patches/2017-10/msg01911.html
	* diagnostic.c (maybe_line_and_column): New.
	(diagnostic_get_location_text): Use it.
	(diagnostic_report_current_module): Likewise.
	(test_diagnostic_get_location_text): Add tests.

	* lib/gcc-dg.exp (process-message): Use -: for no column.
	* c-c++-common/cilk-plus/CK/cilk_for_grain_errors.c: Mark elided
	column messages.
	* c-c++-common/cpp/pr58844-1.c: Likewise.
	* c-c++-common/cpp/pr58844-2.c: Likewise.
	* c-c++-common/cpp/warning-zero-location.c: Likewise.
	* g++.dg/diagnostic/pr77949.C: Likewise.
	* g++.dg/gomp/macro-4.C: Likewise.
	* gcc.dg/Wunknownprag.c: Likewise.
	* gcc.dg/builtin-redefine.c: Likewise.
	* gcc.dg/cpp/Wunknown-pragmas-1.c: Likewise.
	* gcc.dg/cpp/Wunused.c: Likewise.
	* gcc.dg/cpp/misspelled-directive-1.c: Likewise.
	* gcc.dg/cpp/redef2.c: Likewise.
	* gcc.dg/cpp/redef3.c: Likewise.
	* gcc.dg/cpp/redef4.c: Likewise.
	* gcc.dg/cpp/trad/Wunused.c: Likewise.
	* gcc.dg/cpp/trad/argcount.c: Likewise.
	* gcc.dg/cpp/trad/comment-3.c: Likewise.
	* gcc.dg/cpp/trad/comment.c: Likewise.
	* gcc.dg/cpp/trad/defined.c: Likewise.
	* gcc.dg/cpp/trad/directive.c: Likewise.
	* gcc.dg/cpp/trad/funlike-3.c: Likewise.
	* gcc.dg/cpp/trad/funlike.c: Likewise.
	* gcc.dg/cpp/trad/literals-2.c: Likewise.
	* gcc.dg/cpp/trad/macro.c: Likewise.
	* gcc.dg/cpp/trad/pr65238-4.c: Likewise.
	* gcc.dg/cpp/trad/recurse-1.c: Likewise.
	* gcc.dg/cpp/trad/recurse-2.c: Likewise.
	* gcc.dg/cpp/trad/redef2.c: Likewise.
	* gcc.dg/cpp/ucnid-11.c: Likewise.
	* gcc.dg/cpp/unc1.c: Likewise.
	* gcc.dg/cpp/unc2.c: Likewise.
	* gcc.dg/cpp/unc3.c: Likewise.
	* gcc.dg/cpp/unc4.c: Likewise.
	* gcc.dg/cpp/undef2.c: Likewise.
	* gcc.dg/cpp/warn-redefined-2.c: Likewise.
	* gcc.dg/cpp/warn-redefined.c: Likewise.
	* gcc.dg/cpp/warn-unused-macros-2.c: Likewise.
	* gcc.dg/cpp/warn-unused-macros.c: Likewise.
	* gcc.dg/empty-source-2.c: Likewise.
	* gcc.dg/empty-source-3.c: Likewise.
	* gcc.dg/gomp/macro-4.c: Likewise.
	* gcc.dg/noncompile/pr35447-1.c: Likewise.
	* gcc.dg/plugin/location-overflow-test-1.c: Likewise.
	* gcc.dg/pr20245-1.c: Likewise.
	* gcc.dg/pr28419.c: Likewise.
	* gcc.dg/rtl/truncated-rtl-file.c: Likewise.
	* gcc.dg/unclosed-init.c: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@254691 138bc75d-0d04-0410-961f-82ee72b054a4