Fix function amqp_get_monotonic_timestamp return zero
Fix function amqp_get_monotonic_timestamp return zero

On one of my PC (Intel Core2 Duo Processor E7500 2.93 GHz),
QueryPerformanceFrequency return 2933330000.
This value  is greater than AMQP_NS_PER_S (1000000000).

jasonmsoft/rabbitmq-c,Haster2004/rabbitmq-c,tempbottle/rabbitmq-c,jasonmsoft/rabbitmq-c,tempbottle/rabbitmq-c,tempbottle/rabbitmq-c,jqk6/rabbitmq-c,jasonmsoft/rabbitmq-c,kilinrax/rabbitmq-c,jqk6/rabbitmq-c,Haster2004/rabbitmq-c,hjzljp/rabbitmq-c,chenwenbin928/rabbitmq-c,Haster2004/rabbitmq-c,soindy/rabbitmq-c,chenwenbin928/rabbitmq-c,alanxz/rabbitmq-c,sakishum/rabbitmq-c,kilinrax/rabbitmq-c,kilinrax/rabbitmq-c,jqk6/rabbitmq-c,soindy/rabbitmq-c,soindy/rabbitmq-c,hjzljp/rabbitmq-c,jqk6/rabbitmq-c,sakishum/rabbitmq-c,sakishum/rabbitmq-c,hjzljp/rabbitmq-c,hjzljp/rabbitmq-c,jasonmsoft/rabbitmq-c,tempbottle/rabbitmq-c,chenwenbin928/rabbitmq-c,alanxz/rabbitmq-c,alanxz/rabbitmq-c