zstandard: vendor python-zstandard 0.12 The upstream source distribution from PyPI was extracted. Unwanted files were removed. The clang-format ignore list was updated to reflect the new source of files. test-repo-compengines.t was updated to reflect a change in behavior of the zstd library. The project contains a vendored copy of zstandard 1.4.3. The old version was 1.3.8. This should result in some minor performance wins. # no-check-commit because 3rd party code has different style guidelines Differential Revision: https://phab.mercurial-scm.org/D6858

--- a/contrib/python-zstandard/zstd.c	Sun Sep 15 00:07:30 2019 -0400
+++ b/contrib/python-zstandard/zstd.c	Sun Sep 15 20:04:00 2019 -0700
@@ -210,7 +210,7 @@
 	   We detect this mismatch here and refuse to load the module if this
 	   scenario is detected.
 	*/
-	if (ZSTD_VERSION_NUMBER != 10308 || ZSTD_versionNumber() != 10308) {
+	if (ZSTD_VERSION_NUMBER != 10403 || ZSTD_versionNumber() != 10403) {
 		PyErr_SetString(PyExc_ImportError, "zstd C API mismatch; Python bindings not compiled against expected zstd version");
 		return;
 	}