Support Windows; use lsxpack_header v206
- [API] Use lsxpack_header v206.
- [FEATURE] Windows supported.
- [BUGFIX] Fix uninitialized variable use in client (regression in 2.15.0).
- Use ls-hpack 2.2.0.
- Use ls-qpack 2.2.0.
- Sample programs: fix the way maximum number of packets is calculated.
- Remove some dead code.