Namespace our type traits in catch_meta

Previously they could conflict with user-defined type traits that
were in the global namespace.

Fixes #1548

projects/SelfTest/UsageTests/Compilation.tests.cpp

@@ -17,6 +17,11 @@ namespace foo {
     };
 }
 
+namespace bar {
+    template <typename... Ts>
+    struct TypeList {};
+}
+
 #ifdef __GNUC__
 #pragma GCC diagnostic ignored "-Wmissing-declarations"
 #endif
@@ -184,6 +189,11 @@ namespace { namespace CompilationTests {
         STATIC_REQUIRE_FALSE( std::is_void<int>::value );
     }
 
+    TEST_CASE("#1548", "[compilation]") {
+        using namespace bar;
+        REQUIRE(std::is_same<TypeList<int>, TypeList<int>>::value);
+    }
+
 }} // namespace CompilationTests