Update lwIP to latest (2.2.1)

[tjko]

lwIP 2.2.1 released

Would it be possible to update to latest lwIP version? As 2.2.0 has some annoying bugs (like #2214, bug#64685)

[peterharperuk]

Definitely. You can use it yourself in the meantime by specifying PICO_LWIP_PATH to cmake.

[tjko]

Thanks! Looks like fix for #2214 didn't make it in lwIP 2.2.1 release, so PICO_LWIP_PATH is really nice to allow overriding lwIP version bundled with the SDK.

Btw, seems like PICO_LWIP_PATH is not documented anywhere (?) (at least not found in "5.1. Full List of SDK Configuration Defines" in the datasheet/manual).

[kilograham]

ok, let's add docs for that (and friends - e.g. PICO_TINYUSB_PATH, BT?

[kilograham]

merged into develop

[lurch]

Fixed by #2405