v1.4.9
[license] Update year to 2021
fix gitignore
Add basic tracing functionality
[linux-kernel] Update README with initial instructions on how to update zstd in the kernel
Add BtrFS benchmarks
[linux] Write all the patch summaries
[contrib][linux] Add SPDX-License-Identifier
Add linux-kernel freestanding
[kernel] Update README with SquashFS patch
[contrib][linux] Follow style guide more closely