Add more fixes for inavlid memory accesses triggered by corrupt files.

Add more fixes for inavlid memory accesses triggered by corrupt files.

	PR binutils/17531
	* readelf.c (get_data): Avoid allocating memory when we know that
	the read will fail.
	(find_section_by_type): New function.
	(get_unwind_section_word): Check for invalid symbol indicies.
	Check for invalid reloc types.
	(get_32bit_dynamic_section): Add range checks.
	(get_64bit_dynamic_section): Add range checks.
	(process_dynamic_section): Check for a corrupt time value.
	(process_symbol_table): Add range checks.
	(dump_section_as_strings): Add string length range checks.
	(display_tag_value): Likewise.
	(display_arm_attribute): Likewise.
	(display_gnu_attribute): Likewise.
	(display_tic6x_attribute): Likewise.
	(display_msp430x_attribute): Likewise.
	(process_mips_specific): Add range check.