README and SPEC say when a client too slow to send its request line or headers is answered 400 (closes #138)

When SWWAF_CLIENT_REQUEST_TIMEOUT runs out partway through a line, Go's
server reads the part that arrived, a carriage return without its line
feed included, as the whole line. If that part cannot be read as a line,
it answers 400; otherwise it closes the connection without an answer.
The README's "Request log" and SPEC's size and time limits said such a
client always gets no answer, and both documents' summaries of answers
gave 408 for any slow client, when it is only for a slow body.

Model: opus-5-5

README.md

@@ -112,11 +112,11 @@ in `bin/state` unless `SWWAF_STATE_DIR` is set, and the default rule file of
   log line (see `request_id` in "Request log" below).
 - Enforces the timeouts and the size limits below. A limit passed before the
   response has started gets `smallwebwaf`'s own answer: `408` for a client too
-  slow to send its request, `413` for a request body that is too large, `504`
-  for an app too slow to answer, and `502` for a response that is too large or
-  an app that cannot be reached. A request that announces a body over the limit
-  is refused before anything reaches the app. While a request body is still on
-  its way, a request timeout that runs out answers `408` if `smallwebwaf` was
+  slow to send its body, `413` for a request body that is too large, `504` for
+  an app too slow to answer, and `502` for a response that is too large or an
+  app that cannot be reached. A request that announces a body over the limit is
+  refused before anything reaches the app. While a request body is still on its
+  way, a request timeout that runs out answers `408` if `smallwebwaf` was
   waiting for the client to send more, and `504` if it was waiting for the app
   to take what it had. Once the response has started, a limit can only cut the
   connection.
@@ -1042,9 +1042,14 @@ less severe than `SWWAF_LOG_LEVEL` are not written.
 Go's HTTP server, on which `smallwebwaf` is built, reads a request's line and
 headers before `smallwebwaf` sees the request, and some requests end there,
 without a line in the log: headers over `SWWAF_CLIENT_REQUEST_HEADER_MAX_BYTES`,
-which it answers `431`, headers slower than `SWWAF_CLIENT_REQUEST_TIMEOUT`,
-whose connection it closes without an answer, and requests it cannot read at
-all, which it answers itself, mostly with `400`.
+which it answers `431`, requests it cannot read at all, which it answers itself,
+mostly with `400`, and a request line and headers slower than
+`SWWAF_CLIENT_REQUEST_TIMEOUT`. When that time runs out, the server takes what
+has arrived of the line it is reading for the whole line, and answers `400` if
+that is not a line it can read, as for a request line cut before the end of its
+HTTP version, a header cut before its colon, or a line cut between its carriage
+return and line feed. Otherwise, as for a client that stops right after a line
+feed, it closes the connection without an answer.
 
 ### Sending the log to a syslog server