Merged DMD commit c7f94c6b66d3b4233ea01dd3dd9f0028b7118870:

5391 Crash with recursive alias declaration

When a recursive alias declaration is encountered, mark it as
type error (not just as an alias to itself of type error).

dmd/declaration.c

@@ -620,6 +620,7 @@ Dsymbol *AliasDeclaration::toAlias()
     if (inSemantic)
     {   error("recursive alias declaration");
         aliassym = new TypedefDeclaration(loc, ident, Type::terror, NULL);
+        type = Type::terror;
     }
     else if (!aliassym && scope)
         semantic(scope);