ADD: marshmellows new lf command and DetectClock. (works great!)

FIX: a suggested patch for "hf mf csetuid" (https://github.com/Proxmark/proxmark3/issues/35)
FIX: fixed a bug in iso14443a_select_card where the len variable wasnt set,  this made desfire/magic cards not work.

client/uart.c

@@ -73,6 +73,7 @@ serial_port uart_open(const char* pcPortName)
   // Does the system allows us to place a lock on this file descriptor
   if (fcntl(sp->fd, F_SETLK, &fl) == -1) {
     // A conflicting lock is held by another process
+    free(sp);
     return CLAIMED_SERIAL_PORT;
   }