Revert "DI: Fold constant arguments into a single MDString"

This reverts commit r218914 while I investigate some bots.

llvm-svn: 218918
diff --git a/llvm/test/Transforms/Inline/debug-invoke.ll b/llvm/test/Transforms/Inline/debug-invoke.ll
index 0de2d22..41d6074 100644
--- a/llvm/test/Transforms/Inline/debug-invoke.ll
+++ b/llvm/test/Transforms/Inline/debug-invoke.ll
@@ -31,7 +31,7 @@
 }
 
 !llvm.module.flags = !{!1}
-!1 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
+!1 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
 !2 = metadata !{}
 !3 = metadata !{i32 1, i32 0, metadata !2, null}
 !4 = metadata !{i32 2, i32 0, metadata !2, null}