Fix -Weffc++ warnings (GNU 6.3.1)

src/json.hpp.re2c

@@ -6168,6 +6168,21 @@ class basic_json
               thousands_sep(!loc->thousands_sep ? '\0' : loc->thousands_sep[0]),
               decimal_point(!loc->decimal_point ? '\0' : loc->decimal_point[0])
         {}
+        serializer(const serializer& cpy)
+            : o(cpy.o),
+              thousands_sep(cpy.thousands_sep),
+              decimal_point(cpy.decimal_point),
+              loc(cpy.loc),
+              indent_string(cpy.indent_string)
+        {}
+        serializer& operator=(const serializer& rhs) {
+            o = rhs.o;
+            thousands_sep = rhs.thousands_sep;
+            decimal_point = rhs.decimal_point;
+            loc = rhs.loc;
+            indent_string = rhs.indent_string;
+            return *this;
+        }
 
         /*!
         @brief internal implementation of the serialization function

test/src/unit-udt.cpp

@@ -49,16 +49,19 @@ enum class country
 struct age
 {
     int m_val;
+    age(int rhs=0) : m_val(rhs) {}
 };
 
 struct name
 {
     std::string m_val;
+    name(const std::string rhs="") : m_val(rhs) {}
 };
 
 struct address
 {
     std::string m_val;
+    address(const std::string rhs="") : m_val(rhs) {}
 };
 
 struct person
@@ -66,18 +69,24 @@ struct person
     age m_age;
     name m_name;
     country m_country;
+    person() : m_age(),m_name(),m_country() {}
+    person(const age& a, const name& n, const country& c) : m_age(a), m_name(n), m_country(c) {}
 };
 
 struct contact
 {
     person m_person;
     address m_address;
+    contact() : m_person(), m_address() {}
+    contact(const person& p, const address& a) : m_person(p), m_address(a) {}
 };
 
 struct contact_book
 {
     name m_book_name;
     std::vector<contact> m_contacts;
+    contact_book() : m_book_name(), m_contacts() {}
+    contact_book(const name& n, const std::vector<contact>& c) : m_book_name(n), m_contacts(c) {}
 };
 }
 
@@ -319,6 +328,8 @@ namespace udt
 struct legacy_type
 {
     std::string number;
+    legacy_type() : number() {}
+    legacy_type(const std::string& n) : number(n) {}
 };
 }
 
@@ -593,6 +604,8 @@ struct small_pod
 struct non_pod
 {
     std::string s;
+    non_pod() : s() {}
+    non_pod(const std::string& S) : s(S) {}
 };
 
 template <typename BasicJsonType>