Fix initializer list reordering warnings

Caused because initializer list must be in the same order as the member
declarations.

include/mtl/string.hpp

@@ -19,8 +19,8 @@ namespace mtl {
 class istring {
 protected:
 	char* m_str;
-	size_t m_size;
 	size_t m_capacity;
+	size_t m_size;
 
 public:
 	static constexpr const size_t npos = -1;

include/mtl/vector.hpp

@@ -18,8 +18,8 @@ template <typename T>
 class ivector {
 private:
 	T* m_arr;
-	size_t m_size;
 	const size_t m_capacity;
+	size_t m_size;
 
 public:
 	using value_type = T;