Fixed #399

If MSGPACK_DISABLE_LEGACY_CONVERT is defined, msgpack::object::convert(T*) is removed.
Added MSGPACK_DISABLE_LEGACY_CONVERT to build system and documents.

Please define MSGPACK_DISABLE_LEGACY_CONVERT and update your code as follows:
Replace
  int i;
  obj.convert(&i); // Removed pointer version
with
  int i;
  obj.convert(i);  // Reference version

example/cpp03/custom.cpp

@@ -44,7 +44,7 @@ int main(void)
         msgpack::unpack(result, sbuf.str().data(), sbuf.str().size());
         msgpack::object obj = result.get();
 
-        obj.convert(&nc);
+        obj.convert(nc);
 
         std::cout << obj << " value=" << nc.value << " flag=" << nc.flag << std::endl;
     }
@@ -60,7 +60,7 @@ int main(void)
         msgpack::unpack(result, sbuf.str().data(), sbuf.str().size());
         msgpack::object obj = result.get();
 
-        obj.convert(&oc);
+        obj.convert(oc);
 
         std::cout << obj << " value=" << oc.value << std::endl;
     }

example/cpp03/simple.cpp

@@ -40,7 +40,7 @@ int main(void)
     // convert msgpack::object instance into the original type.
     // if the type is mismatched, it throws msgpack::type_error exception.
     msgpack::type::tuple<int, bool, std::string> dst;
-    deserialized.convert(&dst);
+    deserialized.convert(dst);
 
     return 0;
 }

example/cpp03/speed_test.cpp

@@ -50,7 +50,7 @@ void test_map_pack_unpack() {
     std::cout << "Start converting..." << std::endl;
     {
         boost::timer::cpu_timer timer;
-        unpacked.get().convert(&m2);
+        unpacked.get().convert(m2);
         std::string result = timer.format();
         std::cout << result << std::endl;
     }

example/cpp03/speed_test_nested_array.cpp

@@ -73,7 +73,7 @@ void test_array_of_array() {
     std::cout << "Start converting..." << std::endl;
     {
         boost::timer::cpu_timer timer;
-        unpacked.get().convert(&v2);
+        unpacked.get().convert(v2);
         std::string result = timer.format();
         std::cout << result << std::endl;
     }