Explicitly default copy ctors for some classes

This fixes -Wdeprecated-copy with FreeBSD's clang17.

This commit reverts a change from 8a32b0b3d4, where a private copy
assignment operator was deleted, whereas it was needed to explicitly
declare the copy constructor, refs #5294.

source/ps/CStrIntern.cpp

@@ -34,6 +34,8 @@ public:
 // 		LOGWARNING("New interned string '%s'", data.c_str());
 	}
 
+	CStrInternInternals(const CStrInternInternals& b) = default;
+
 	bool operator==(const CStrInternInternals& b) const
 	{
 		// Compare hash first for quick rejection of inequal strings

source/tools/atlas/GameInterface/MessagesSetup.h

@@ -91,8 +91,9 @@ const bool NOMERGE = false;
 #define COMMANDDATASTRUCT(t) \
 	struct d##t { \
 	private: \
-		d##t& operator=(const d##t&) = delete; \
-	public:
+		const d##t& operator=(const d##t&); \
+	public: \
+		d##t(const d##t& d) = default;
 
 #define COMMANDSTRUCT(t, merge) \
 	struct m##t : public mWorldCommand, public d##t { \