Two el_runtime portability defects only ever lived in staged local copies
used to hand-build neuron-ui PR #136's curl-enabled Windows neuron.exe.
gcc 15 promotes both to hard errors, so a clean el checkout cannot rebuild
that soul. Upstream the minimal fixes so the build is reproducible:
- http_serve_async: cast setsockopt optval to (const char*). Win32/mingw
setsockopt wants const char*, not int*; the cast is a no-op on POSIX and
matches the four already-cast sites elsewhere in this file.
- engram_save persist path: map fsync -> _commit in the _WIN32-only
el_platform_win.h (io.h already included). Windows has no fsync(); the
POSIX path is untouched.