Modernize various files (src/m*) (#6267)

* Modernize various files (src/m*)

* range-based for loops
* code style
* C++ headers instead of C headers
* Default operators
* empty function

Thanks to clang-tidy

src/mods.h

@@ -121,7 +121,7 @@ private:
 	std::unordered_set<std::string> m_name_conflicts;
 
 	// Deleted default constructor
-	ModConfiguration() {}
+	ModConfiguration() = default;
 
 };
 
@@ -155,7 +155,7 @@ class ModMetadata: public Metadata
 {
 public:
 	ModMetadata(const std::string &mod_name);
-	~ModMetadata() {}
+	~ModMetadata() = default;
 
 	virtual void clear();