Merge pull request #561 from pkubaj/patch-1

Fix build on architectures with unsigned char

pnet_datalink/src/bpf.rs

@@ -129,7 +129,7 @@ pub fn channel(network_interface: &NetworkInterface, config: Config) -> io::Resu
     }
     let mut iface: bpf::ifreq = unsafe { mem::zeroed() };
     for (i, c) in network_interface.name.bytes().enumerate() {
-        iface.ifr_name[i] = c as i8;
+        iface.ifr_name[i] = c as libc::c_char;
     }
 
     let buflen = config.read_buffer_size as libc::c_uint;