Fix: Include cstring in socket_stream.cc
Fix: Include cstring in socket_stream.cc

Fix errors like:
  socket_stream.cc:62:23: error: ‘strerror’ is not a member of ‘std’

No-Docs-Update-Reason: bugfix

Change-Id: I40b559a9c0fdff4ce7700af8f788571fdf510fc3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/56900
Reviewed-by: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Reviewed-by: Michael Spang <e1fb1a05abba8fb04acbcbe6d766da7764320db0@google.com>
Commit-Queue: Rob Oliver <a5e5d1b61ce0a2226e72fcc143bfa649e214acf1@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed