reporters: silence -Wsubobject-linkage

gcc emits `Wsubobject-linkage`, because the the publicly visible
`TablePrinter` contains `ColumnInfo`, which is part of an anonymous
namespace

src/catch2/reporters/catch_reporter_console.cpp

@@ -209,13 +209,6 @@ findMax( std::size_t& i, std::size_t& j, std::size_t& k, std::size_t& l ) {
         return l;
 }
 
-enum class Justification { Left, Right };
-
-struct ColumnInfo {
-    std::string name;
-    std::size_t width;
-    Justification justification;
-};
 struct ColumnBreak {};
 struct RowBreak {};
 struct OutputFlush {};
@@ -293,6 +286,14 @@ class Duration {
 };
 } // end anon namespace
 
+enum class Justification { Left, Right };
+
+struct ColumnInfo {
+    std::string name;
+    std::size_t width;
+    Justification justification;
+};
+
 class TablePrinter {
     std::ostream& m_os;
     std::vector<ColumnInfo> m_columnInfos;