* dwarf2dbg.h (struct dwarf2_line_info): Add discriminator field.
	* dwarf2dbg.c (current): Add discriminator field.
	(dwarf2_where): Copy discriminator value.
	(dwarf2_consume_line_info): Set discriminator to 0.
	(dwarf2_directive_loc): Process discriminator sub-op.
	(out_leb128): New function.
	(process_entries): Output DW_LNE_set_discriminator.
	* doc/as.texinfo: Add discriminator operand to .loc directive.
	* testsuite/gas/lns/lns-common-1.d: Add test for discriminator.
	* testsuite/gas/lns/lns-common-1.s: Likewise.