bug #42662 clang warnings under FreeBSD 10.x

* avrftdi.c: remove warnings
* buspirate.c: (Dito.)
* dfu.c: (Dito.)
* fileio.c: (Dito.)
* libavrdude.h: (Dito.)
* pickit2.c: (Dito.)
* safemode.c: (Dito.)
* ser_avrdoper.c: (Dito.)
* ser_posix.c: (Dito.)
* ser_win32.c: (Dito.)
* stk500v2.c: (Dito.)
* usb_libusb.c: (Dito.)
* usbasp.c: (Dito.)

* config_gram.y: fix problem when using parent part with usbpid lists
                 (existing list was extended not overwritten)



git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@1328 81a1dc3b-b13d-400b-aceb-764788c761c2

dfu.c

@@ -139,7 +139,8 @@ struct dfu_dev * dfu_open(char *port_spec)
   if (dfu == NULL)
   {
     avrdude_message(MSG_INFO, "%s: out of memory\n", progname);
-    return 0;
+    free(bus_name);
+    return NULL;
   }
 
   dfu->bus_name = bus_name;