Installation of new headers

Added below headers to installation:
MQTTProperties.h MQTTReasonCodes.h MQTTSubscribeOpts.h
as they are needed during build process.
Signed-off-by: Krzysztof Bogucki <kristofbo@gmail.com>

src/CMakeLists.txt

@@ -102,7 +102,7 @@ IF (PAHO_BUILD_STATIC)
         ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
 ENDIF()
 
-INSTALL(FILES MQTTAsync.h MQTTClient.h MQTTClientPersistence.h
+INSTALL(FILES MQTTAsync.h MQTTClient.h MQTTClientPersistence.h MQTTProperties.h MQTTReasonCodes.h MQTTSubscribeOpts.h
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
 IF (PAHO_WITH_SSL)