Support DWARF discriminators in object streamer.

Summary:
This adds support for emitting DWARF path discriminator values in
the object streamer. It also changes the DWARF dumper to show
discriminator values in the line table output.

Reviewers: echristo

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2794

llvm-svn: 201427
diff --git a/llvm/test/MC/MachO/gen-dwarf-cpp.s b/llvm/test/MC/MachO/gen-dwarf-cpp.s
index e42a63a..69c49c6 100644
--- a/llvm/test/MC/MachO/gen-dwarf-cpp.s
+++ b/llvm/test/MC/MachO/gen-dwarf-cpp.s
@@ -17,6 +17,6 @@
 // CHECK: file_names[  2]    0 0x00000000 0x00000000 t.s
 
 // We check that the source line number 100 is picked up before the "movl"
-// CHECK: Address            Line   Column File   ISA Flags
-// CHECK: ------------------ ------ ------ ------ --- -------------
-// CHECK: 0x0000000000000000    102      0      2   0  is_stmt
+// CHECK: Address            Line   Column File   ISA Discriminator Flags
+// CHECK: ------------------ ------ ------ ------ --- ------------- -------------
+// CHECK: 0x0000000000000000    102      0      2   0             0  is_stmt