Fix warnings in ExtraTests and Examples

tests/ExtraTests/X01-PrefixedMacros.cpp

@@ -11,11 +11,13 @@
 #include <type_traits>
 #include <stdexcept>
 
-[[noreturn]]
-void this_throws() {
-    throw std::runtime_error("Some msg");
+namespace {
+    [[noreturn]]
+    void this_throws() {
+        throw std::runtime_error("Some msg");
+    }
+    void this_doesnt_throw() {}
 }
-void this_doesnt_throw() {}
 
 CATCH_TEST_CASE("PrefixedMacros") {
     using namespace Catch::Matchers;

tests/ExtraTests/X11-DisableStringification.cpp

@@ -7,9 +7,11 @@
 #include <catch2/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
-struct Hidden {};
+namespace {
+    struct Hidden {};
 
-bool operator==(Hidden, Hidden) { return true; }
+    bool operator==(Hidden, Hidden) { return true; }
+}
 
 TEST_CASE("DisableStringification") {
     REQUIRE( Hidden{} == Hidden{} );