DebugInfo: GDBIndexEntry*String conversion functions now return const char* for easy llvm::formating

This was previously invoking UB by passing a user-defined type to
format. Thanks to Jordan Rose for pointing this out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191060 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Dwarf.cpp b/lib/Support/Dwarf.cpp
index 0e64035..f499345 100644
--- a/lib/Support/Dwarf.cpp
+++ b/lib/Support/Dwarf.cpp
@@ -742,7 +742,7 @@
   return 0;
 }
 
-StringRef llvm::dwarf::GDBIndexEntryKindString(GDBIndexEntryKind Kind) {
+const char *llvm::dwarf::GDBIndexEntryKindString(GDBIndexEntryKind Kind) {
   switch (Kind) {
   case GIEK_NONE:
     return "NONE";
@@ -764,7 +764,7 @@
   llvm_unreachable("Unknown GDBIndexEntryKind value");
 }
 
-StringRef llvm::dwarf::GDBIndexEntryLinkageString(GDBIndexEntryLinkage Linkage) {
+const char *llvm::dwarf::GDBIndexEntryLinkageString(GDBIndexEntryLinkage Linkage) {
   switch (Linkage) {
   case GIEL_EXTERNAL:
     return "EXTERNAL";