Merge pull request mfontanini#305 from yuanchunchen/fix-win-link-error-lnk2019

ADD dllexport front of HandleDeleter, to Fix link error in win dll usage.

Author: mfontanini

include/cppkafka/kafka_handle_base.h

@@ -369,7 +369,7 @@ class CPPKAFKA_API KafkaHandleBase {
 private:
     static const std::chrono::milliseconds DEFAULT_TIMEOUT;
 
-    struct HandleDeleter {
+    struct CPPKAFKA_API HandleDeleter {
         explicit HandleDeleter(const KafkaHandleBase* handle_base_ptr) : handle_base_ptr_{handle_base_ptr} {}
         void operator()(rd_kafka_t* handle);
     private: