PR gas/12011

	PR gas/12011
	* config/obj-elf.c (obj_elf_parse_section_letters): Correct test
	for error return from md_elf_section_letter.
	* config/tc-alpha.c (alpha_elf_section_letter): Correct error message.
	* config/tc-i386.c (x86_64_section_letter): Likewise.
	* config/tc-ia64.c (ia64_elf_section_letter): Likewise.
	* config/tc-mep.c (mep_elf_section_letter): Likewise.
	* gas/elf/bad-section-flag.d, * gas/elf/bad-section-flag.err,
	* gas/elf/bad-section-flag.s: New test.
	* gas/elf/elf.exp: Run it.