Fix undefined behaviour in utf16_to_utf8

Fixes SqliteModernCpp#151.

Author: zauguin

hdr/sqlite_modern_cpp/utility/utf16_utf8.h

@@ -2,6 +2,7 @@
 
 #include <locale>
 #include <string>
+#include <algorithm>
 
 #include "../errors.h"
 
@@ -10,7 +11,7 @@ namespace sqlite {
 		inline std::string utf16_to_utf8(const std::u16string &input) {
 			struct : std::codecvt<char16_t, char, std::mbstate_t> {
 			} codecvt;
-			std::mbstate_t state;
+			std::mbstate_t state{};
 			std::string result((std::max)(input.size() * 3 / 2, std::size_t(4)), '\0');
 			const char16_t *remaining_input = input.data();
 			std::size_t produced_output = 0;