Fix memory leak in keybinder_bind_full

Resources allocated by XkbGetMap() should be freed by XkbFreeKeyboard.
Otherwise I get the following leaked memory report from Valgrind:

==14972== 1,920 bytes in 48 blocks are definitely lost in loss record 1,598 of 1,626
==14972==    at 0x402C118: calloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==14972==    by 0x5064EA8: XkbGetMap (in /usr/lib/i386-linux-gnu/libX11.so.6.3.0)
==14972==    by 0x428019D: grab_ungrab (bind.c:203)
==14972==    by 0x4280320: do_grab_key (bind.c:326)
==14972==    by 0x4280721: keybinder_bind_full (bind.c:574)
==14972==    by 0x4280791: keybinder_bind (bind.c:539)
==14972==    by 0x8049220: xvd_keys_init (xvd_keys.c:141)
==14972==    by 0x8048F84: main (main.c:126)

libkeybinder/bind.c

@@ -243,7 +243,7 @@ grab_ungrab (GdkWindow *rootwin,
 
 	}
 	g_free(keys);
-	XkbFreeClientMap(xmap, 0, TRUE);
+	XkbFreeKeyboard(xmap, 0, TRUE);
 
 	return success;
 }