Revert "Revert "DI: LLVM schema change: fold constants into string""

This reverts commit r218917, effectively reapplying r218913.  Original
commit message follows.

--

Update debug info testcases for an LLVM metadata schema change to fold
metadata constant operands into a single `MDString`.

Part of PR17891.

llvm-svn: 219011
diff --git a/clang/test/CodeGenCXX/debug-info-zero-length-arrays.cpp b/clang/test/CodeGenCXX/debug-info-zero-length-arrays.cpp
index 1017965..144c476 100644
--- a/clang/test/CodeGenCXX/debug-info-zero-length-arrays.cpp
+++ b/clang/test/CodeGenCXX/debug-info-zero-length-arrays.cpp
@@ -7,6 +7,6 @@
 A a;
 
 // CHECK: metadata [[ARRAY_TYPE:![0-9]*]]} ; [ DW_TAG_member ] [x]
-// CHECK: metadata [[ELEM_TYPE:![0-9]*]], i32 0, null, null, null} ; [ DW_TAG_array_type ] [line 0, size 0, align 32, offset 0] [from int]
+// CHECK: metadata !{metadata !"0x1\00\000\000\0032\000\000\000", null, null, metadata {{![0-9]+}}, metadata [[ELEM_TYPE:![0-9]+]], null, null, null} ; [ DW_TAG_array_type ] [line 0, size 0, align 32, offset 0] [from int]
 // CHECK: [[ELEM_TYPE]] = metadata !{metadata [[SUBRANGE:.*]]}
-// CHECK: [[SUBRANGE]] = metadata !{i32 786465, i64 0, i64 -1} ; [ DW_TAG_subrange_type ] [unbounded]
+// CHECK: [[SUBRANGE]] = metadata !{metadata !"0x21\000\00-1"} ; [ DW_TAG_subrange_type ] [unbounded]