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/lib/DebugInfo/DWARFDebugLine.h b/llvm/lib/DebugInfo/DWARFDebugLine.h
index 2990756..9e93cc8 100644
--- a/llvm/lib/DebugInfo/DWARFDebugLine.h
+++ b/llvm/lib/DebugInfo/DWARFDebugLine.h
@@ -112,6 +112,9 @@
     // An unsigned integer whose value encodes the applicable instruction set
     // architecture for the current instruction.
     uint8_t Isa;
+    // An unsigned integer representing the DWARF path discriminator value
+    // for this location.
+    uint32_t Discriminator;
     // A boolean indicating that the current instruction is the beginning of a
     // statement.
     uint8_t IsStmt:1,