Remote: explicitly qualify type

When building the remote mirror for Windows, the build would fail due to the
symbol resolution being slightly different on Windows.  Explicitly qualify the
name to resolve the ambiguity.  This reapirs the build of the remote mirror for
Windows.

Author: compnerd

include/swift/Remote/MetadataReader.h

@@ -1528,7 +1528,7 @@ class MetadataReader {
     if (!demangling)
       return nullptr;
 
-    NodePointer top;
+    Demangle::NodePointer top;
     // References to type nodes behave as types in the mangling.
     if (isa<TargetTypeContextDescriptor<Runtime>>(descriptor.getLocalBuffer()) ||
         isa<TargetProtocolDescriptor<Runtime>>(descriptor.getLocalBuffer())) {