Rename Mongoose constants: NS_ -> MG_, NSF_ -> MG_F_

examples/api_server/api_server.c

examples/arduino_restful_client/arduino_restful_client.ino

examples/arduino_restful_server/arduino_restful_server.ino

examples/captive_dns_server/Makefile

examples/captive_dns_server/captive_dns_server.c

examples/coap_client/Makefile

examples/coap_client/coap_client.c

examples/coap_server/Makefile

examples/coap_server/coap_server.c

examples/http_client/Makefile

examples/http_client/http_client.c

examples/json_rpc_server/json_rpc_server.c

examples/load_balancer/Dockerfile

examples/load_balancer/Makefile

examples/load_balancer/load_balancer.c

examples/mqtt_broker/Makefile

examples/mqtt_client/Makefile

examples/mqtt_client/mqtt_client.c

examples/multithreaded_restful_server/Makefile

...ltithreaded_restful_server/multithreaded_restful_server.c