This sources was obtained from upstream github and then repacked.
Most vendored libs was removed (to reduce space and fix some possible issues
with buildscripts using files (e.g. headers) from contrib dir even when
system ones exists.

libbtrie and murmurhash was left in contrib since they are not really separate
libs but a small part of bigger projects not intented to be packed into Debian
archive (libbtrie is demo realization and murmuhash is part of hash benchmark
project).

cityhash102 is the copy of Google's cityhash project version 1.0.2. We could not
pack and use debianized CityHash library, because ClickHouse strictly need this
particular version of cityhash algorithm, not the latest upstream (which uses
incompatible hash function).

 We also remove website and docs/tools/mkdocs-material-theme, because they
 contain some generated files (JS, CSS, images) without sources or files under
 trademark protection).

website and docs/tools/mkdocs-material-theme was removed because is contains
many generated files (JS, CSS, images) without sources and files which are
non-free or under trademark protection.
