doc: net: fix typo in example code
build: include postmortem symbols on linux

Previously we were building the symbols, but the linker was garbage
collecting the symbols because they weren't used. Inform the linker
that we want to keep all symbols from v8 around.
tls: reset NPN callbacks after SNI

SNI callback selects a new SSL_CTX for the connection, which doesn't
have NPN callbacks set up.
tls: fix pool usage race

When calling `encOut` in loop, `maybeInitFinished()` may invoke
`clearOut`'s loop, leading to the writing of interleaved data
(encrypted and cleartext) into the one shared pool.

Move `maybeInitFinished()` out of the loop and add assertion for
future.