* std.Io.Reader: fix confused semantics of rebase. Before it was
ambiguous whether it was supposed to be based on end or seek. Now it
is clearly based on seek, with an added assertion for clarity.
* std.crypto.tls.Client: fix panic due to not enough buffer size
available. Also, avoid unnecessary rebasing.
* std.http.Reader: introduce max_head_len to limit HTTP header length.
This prevents crash in underlying reader which may require a minimum
buffer length.
* std.http.Client: choose better buffer sizes for streams and TLS
client. Crucially, the buffer shared by HTTP reader and TLS client
needs to be big enough for all http headers *and* the max TLS record
size. Bump HTTP header size default from 4K to 8K.
fixes#24872
I have noticed however that there are still fetch problems
a0f9a5e78d