Major changes, including Brotli and Lizard

- update of zstd-mt library
- add brotli v0.6.0
- add lizard v2.0
- xxhash is from zstd for lz4, lz5 and lizard now
- update also the documentation, where needed

C/zstd/LICENSE

@@ -0,0 +1,30 @@
+BSD License
+
+For Zstandard software
+
+Copyright (c) 2016-present, Facebook, Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * Neither the name Facebook nor the names of its contributors may be used to
+   endorse or promote products derived from this software without specific
+   prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

C/zstd/README.md

@@ -0,0 +1,85 @@
+Zstandard library files
+================================
+
+The __lib__ directory contains several directories.
+Depending on target use case, it's enough to include only files from relevant directories.
+
+
+#### API
+
+Zstandard's stable API is exposed within [zstd.h](zstd.h),
+at the root of `lib` directory.
+
+
+#### Advanced API
+
+Some additional API may be useful if you're looking into advanced features :
+- common/error_public.h : transforms `size_t` function results into an `enum`,
+                          for precise error handling.
+- ZSTD_STATIC_LINKING_ONLY : if you define this macro _before_ including `zstd.h`,
+                          it will give access to advanced and experimental API.
+                          These APIs shall ___never be used with dynamic library___ !
+                          They are not "stable", their definition may change in the future.
+                          Only static linking is allowed.
+
+#### ZSTDMT API
+
+To enable multithreaded compression within the library, invoke `make lib-mt` target.
+Prototypes are defined in header file `compress/zstdmt_compress.h`.
+When linking a program that uses ZSTDMT API against libzstd.a on a POSIX system,
+`-pthread` flag must be provided to the compiler and linker.
+Note : ZSTDMT prototypes can still be used with a library built without multithread support,
+but in this case, they will be single threaded only.
+
+#### Modular build
+
+Directory `common/` is required in all circumstances.
+You can select to support compression only, by just adding files from the `compress/` directory,
+In a similar way, you can build a decompressor-only library with the `decompress/` directory.
+
+Other optional functionalities provided are :
+
+- `dictBuilder/`  : source files to create dictionaries.
+                    The API can be consulted in `dictBuilder/zdict.h`.
+                    This module also depends on `common/` and `compress/` .
+
+- `legacy/` : source code to decompress previous versions of zstd, starting from `v0.1`.
+              This module also depends on `common/` and `decompress/` .
+              Library compilation must include directive `ZSTD_LEGACY_SUPPORT = 1` .
+              The main API can be consulted in `legacy/zstd_legacy.h`.
+              Advanced API from each version can be found in their relevant header file.
+              For example, advanced API for version `v0.4` is in `legacy/zstd_v04.h` .
+
+
+#### Using MinGW+MSYS to create DLL
+
+DLL can be created using MinGW+MSYS with the `make libzstd` command.
+This command creates `dll\libzstd.dll` and the import library `dll\libzstd.lib`.
+The import library is only required with Visual C++.
+The header file `zstd.h` and the dynamic library `dll\libzstd.dll` are required to
+compile a project using gcc/MinGW.
+The dynamic library has to be added to linking options.
+It means that if a project that uses ZSTD consists of a single `test-dll.c`
+file it should be linked with `dll\libzstd.dll`. For example:
+```
+    gcc $(CFLAGS) -Iinclude/ test-dll.c -o test-dll dll\libzstd.dll
+```
+The compiled executable will require ZSTD DLL which is available at `dll\libzstd.dll`.
+
+
+#### Obsolete streaming API
+
+Streaming is now provided within `zstd.h`.
+Older streaming API is still available within `deprecated/zbuff.h`.
+It will be removed in a future version.
+Consider migrating code towards newer streaming API in `zstd.h`.
+
+
+#### Miscellaneous
+
+The other files are not source code. There are :
+
+ - LICENSE : contains the BSD license text
+ - Makefile : script to compile or install zstd library (static and dynamic)
+ - libzstd.pc.in : for pkg-config (`make install`)
+ - README.md : this file