I have made the following code:

#include "arduino.h"
extern "C" {
  #include "mesh.h"
}
void ESP8266_enabled_callback()
{
}
void setup() {
    espconn_mesh_enable(ESP8266_enabled_callback, mesh_type::MESH_LOCAL);
}
void loop() {
}

When I build the code I get the following error:

EPS_MESH_TEST.cpp.o:(.text.setup+0x4): undefined reference to espconn_mesh_enable' EPS_MESH_TEST.cpp.o: In functionsetup':
C:\arduino-1.6.5-r2/EPS_MESH_TEST.ino:11: undefined reference to `espconn_mesh_enable'
collect2.exe: error: ld returned 1 exit status
Fejl i kompilering.

What do I or the framework doing wrong?