Header validation, recvmmsg, edge case fixes
- [FIX] Content-length check in QPACK decoder handler.
- [FIX] HTTP/1.x module: stricter validation for field names and values.
- [FIX] Sample tools: fix recvmmsg receive batching (issue #434).
- [FIX] crypto object ownership on promotion failure.
- [IMPROVEMENT] Use ls-hpack v2.3.5.