Compliance: Ignore unused chunk-extensions to correctly handle large ones.

Compliance: Ignore unused chunk-extensions to correctly handle large ones.

Chunk parser did not advance until it got a complete chunk-extension.
HttpStateData::maybeReadVirginBody() does not grow the buffer if there is no
space available for the [chunked] body so the transaction with a large
chunk-extension would stall. The default HttpStateData input buffer size is
just 2KB so it does not take a "very large" extension to stall the
transaction.

Somewhat ironically, we are not even interested in the HTTP chunk-extension
itself. After the change, Squid skips the chunk-extension data as soon as it
gets it (except for the last-chunk, see below). Incrementally ignoring data
requires handling quoted strings correctly, to avoid mis-detecting a quoted
CRLF. Thus, we now preserve the quoted string parsing state in
ChunkedCodingParser.

Last-chunk chunk-extension is useful for ICAP. We parse it instead of
ignoring. This parsing is done as before and may still lead to connection
hanging, but a proper fix is outside this patch scope. Similarly, other
stalling reasons are outside this patch scope.

Co-Advisor test case:
    test_case/rfc2616/chunked-1p0-longValExt-16385-toClt