57: Heap out-of-bounds read in `curl_easy_escape_ccsid()` / `curl_easy_unescape_ccsid()`

`curl_easy_escape_ccsid()` and `curl_easy_unescape_ccsid()` in `projects/OS400/ccsidcurl.c` discard the converted byte count returned by `dynconvert()` and pass `0` to the downstream `curl_easy_escape()` / `curl_easy_unescape()`. When the caller supplies a positive explicit `length` with …

// curl_easy_escape_ccsid — line 283
s = dynconvert(ASCII_CCSID, string, length ? length : -1, sccsid, NULL);
// ...
d = curl_easy_escape(handle, s, 0);   // line 288 — 0 means strlen()

// curl_easy_unescape_ccsid — line 312
s = dynconvert(ASCII_CCSID, string, length ? length : -1, sccsid, NULL); …