di-longlong64-sync-1.c: Add comments to checks for multiple messages reported for one line of source code.

	* gcc.dg/di-longlong64-sync-1.c: Add comments to checks for multiple
	messages reported for one line of source code.
	* gcc.dg/format/few-1.c: Likewise.
	* gcc.dg/ia64-sync-2.c: Likewise.
	* gcc.dg/sync-2.c: Likewise.
	* gcc.dg/noncompile/pr44517.c: Likewise.

From-SVN: r188537