PR29171, invalid read causing SIGSEGV

The fix here is to pass "section" down to read_and_display_attr_value.
The test in read_and_display_attr_value is a little bit of hardening.

	PR 29171
	* dwarf.c (display_debug_macro, display_debug_names): Pass section
	to read_and_display_attr_value2.
	(read_and_display_attr_value): Don't attempt to check for .dwo
	section name when section is NULL.