Define `ssize_t` for MSVC builds
Define `ssize_t` for MSVC builds

Signed-off-by: Michael Steinert <ff2bcd618b500c74b38137be3a6709962e7b76df@gmail.com>

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