websockets, check for negative payload lengths

[icing]

• in en- and decoding, check the websocket frame payload lengths for negative values (from curl_off_t) and error the operation in that case

[bagder]

Except that ASAN complains on the new test:

ws.c:228:52: runtime error: left shift of 255 by 56 places cannot be represented in type 'curl_off_t' (aka 'long')

[jay]

lgtm but hyper ci is failing:

test 2307...[WebSockets, overlong PING payload]

lib2302 returned 52, when expecting 23
 2307: exit FAILED

[bagder]

lib2302 returned 52, when expecting 23

it is really complicated sometimes to get the same error codes for hyper but 52 (CURLE_GOT_NOTHING) seems wrong.

[icing]

lib2302 returned 52, when expecting 23

it is really complicated sometimes to get the same error codes for hyper but 52 (CURLE_GOT_NOTHING) seems wrong.

I declare test 2307 does not work with hyper at all. Nowhere do I see the server response data being processed. Change my mind.

[bagder]

@icing: this new test 2307 seems to be flaky and has already failed for me locally and in CI builds after this...