Add support outbox, changed API

lib/platform_esp32_idf.c

@@ -0,0 +1,30 @@
+#include "platform.h"
+
+#ifdef ESP_PLATFORM
+#include "esp_system.h"
+#include <sys/time.h>
+
+char *platform_create_id_string()
+{
+    uint8_t mac[6];
+    char *id_string = calloc(1, 32);
+    mem_assert(id_string);
+    esp_read_mac(mac, ESP_MAC_WIFI_STA);
+    sprintf(id_string, "ESP32_%02x%02X%02X", mac[3], mac[4], mac[5]);
+    return id_string;
+}
+
+int platform_random(int max)
+{
+    return esp_random()%max;
+}
+
+int platform_tick_get_ms()
+{
+    struct timeval te;
+    gettimeofday(&te, NULL); // get current time
+    long long milliseconds = te.tv_sec*1000LL + te.tv_usec/1000; // calculate milliseconds
+    // printf("milliseconds: %lld\n", milliseconds);
+    return milliseconds;
+}
+#endif