DebugInfo: Remove DIScope

Replace uses of `DIScope` with `MDScope*`.  There was one spot where
I've left an `MDScope*` uninitialized (where `DIScope` would have been
default-initialized to `nullptr`) -- this is intentional, since the
if/else that follows should unconditional assign it to a value.

llvm-svn: 235327
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 9484bb6..f197d22 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -183,10 +183,11 @@
   }
 
   /// Add a new global name to the compile unit.
-  void addGlobalName(StringRef Name, DIE &Die, DIScope Context) override;
+  void addGlobalName(StringRef Name, DIE &Die, const MDScope *Context) override;
 
   /// Add a new global type to the compile unit.
-  void addGlobalType(DIType Ty, const DIE &Die, DIScope Context) override;
+  void addGlobalType(const MDType *Ty, const DIE &Die,
+                     const MDScope *Context) override;
 
   const StringMap<const DIE *> &getGlobalNames() const { return GlobalNames; }
   const StringMap<const DIE *> &getGlobalTypes() const { return GlobalTypes; }