partially revert "Switch to copy-and-swap idiom for operator=."

This partially reverts commit 45cd949.

Ignored ValueInternal* changes, since those did not produce symbols for
Debian build. (They must not have used the INTERNAL stuff.)

Ignored CZString changes since those are private (and sizeof struct did
not change).

  #78

Conflicts:
	include/json/value.h
	src/lib_json/json_internalarray.inl
	src/lib_json/json_internalmap.inl
	src/lib_json/json_value.cpp

Author: cdunn2001

Diff for: include/json/value.h

@@ -256,7 +256,7 @@ Json::Value obj_value(Json::objectValue); // {}
   ~Value();
 
   // Deep copy, then swap(other).
-  Value& operator=(Value other);
+  Value &operator=(const Value &other);
   /// Swap everything.
   void swap(Value& other);
   /// Swap values but leave comments and source offsets in place.

Diff for: src/lib_json/json_value.cpp

@@ -425,8 +425,9 @@ Value::~Value() {
     delete[] comments_;
 }
 
-Value& Value::operator=(Value other) {
-  swap(other);
+Value &Value::operator=(const Value &other) {
+  Value temp(other);
+  swap(temp);
   return *this;
 }