Fix nREPL on Windows; add a version string

The nREPL server bound its loopback socket through libc process symbols,
which don't carry the socket entry points on Windows — they live in
ws2_32.dll and aren't in joltc.exe's export table, so --nrepl-server died
with "no entry for socket". Load ws2_32 before the foreign bindings there,
call WSAStartup once, and use Winsock's closesocket and int-typed
recv/send. Also fix SOL_SOCKET/SO_REUSEADDR, which the old macos-only
check got wrong on Windows.

Bake a version string into the self-contained binary at build time (from
$JOLT_VERSION, else git describe) and expose it via jolt.host/jolt-version:
--version / -V print it, and it shows in --help, the repl banner, and the
nREPL startup line. Dev runs off bin/joltc read it from git describe.

Add -e to the help output.

bin/joltc

@@ -14,5 +14,7 @@
 # JOLT_PWD.
 root="$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)"
 export JOLT_PWD="${JOLT_PWD:-$PWD}"
+# Version for --version / banners: git describe of this checkout, else "dev".
+export JOLT_VERSION="${JOLT_VERSION:-$(git -C "$root" describe --tags --always --dirty 2>/dev/null || echo dev)}"
 cd "$root" || exit 1
 exec chez --script host/chez/cli.ss "$@"