Here is a follow-on patch.  I noticed that dwarf2_emit_label() can also use the 
new dwarf2_consume_line_info function.

Is this OK?

I forgot to say how I tested this.  I built binutils for xtensa-elf, 
ia64-unknown-linux-gnu and i686-pc-linux-gnu targets, all hosted on 
i686-pc-linux-gnu, and ran the testsuite.  I've rerun those tests now with this 
follow-on patch.  Everything passed as expected with one exception: the 
ld-ia64/line.exp test fails but I see the same failure without any of my 
changes.  ld fails to show the source line number in an error message.  That 
does seem suspicious.  Is this a known problem?

gas/
	* dwarf2dbg.c (dwarf2_emit_label): Use dwarf2_consume_line_info.