Restore readelf's string dump to previous behaviour where newlines were caused line breaks.

	PR 25543
	* readelf.c (dump_section_as_strings): Display new-line characters
	as \n and then insert a line break.
	* testsuite/binutils-all/pr25543.s: New test.
	* testsuite/binutils-all/pr25543.d: Test driver.
	* testsuite/binutils-all/readelf.exp: Run the new test.