Update to support some older, encrytped APEs

Some APEs report their am value as something like `AirPort4,107` (Old
version) or `AirPort10,115` (new version). (There is some evidence in
the player.c code that some old APEs do not report an AM value at all,
but all three of mine do.

As far as I can tell, the following is true of APEs with AM values:
- am="AirPort4..." - Encrypted (so devtype should remove
`RAOP_DEV_APEX_80211N`)
- am="Airport10..." - Not encrypted (so devtype should be set to
`OTHER`)

So, I suggest the following change to line 28:
```
else if (strncmp(p, "AirPort4", strlen("AirPort4")) != 0)
```

There may be other flavors of APEs that may fail this test, but it's
the best I can suggest with the devices I have.