Fixed an erroneous usage of LLVM cast with a regular C++ type.

Only found with debug-mode LLVM build.

src/CppParser/Parser.cpp

@@ -1809,7 +1809,7 @@ DeclarationContext* Parser::GetNamespace(const clang::Decl* D,
         {
             auto D = cast<Decl>(Ctx);
             auto Decl = WalkDeclaration(D);
-            DC = cast<DeclarationContext>(Decl);
+            DC = static_cast<DeclarationContext*>(Decl);
         } }
     }