Explode zstd 1.4.5 into separate upstream files

It's much nicer to import from upstream this way, and compiles
faster too.

Everything in lib/ is unmodified 1.4.5.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #12978

module/zstd/include/string.h

@@ -44,6 +44,7 @@ extern "C" {
 #ifdef _KERNEL
 
 #if defined(__FreeBSD__)
+#include <sys/types.h>    /* u_int, u_char */
 #include <sys/systm.h>    /* memcpy, memset */
 #elif defined(__linux__)
 #include <linux/string.h> /* memcpy, memset */

module/zstd/include/zstd_compat_wrapper.h

@@ -45,6 +45,20 @@
  * nm zstd.o | awk '{print "#define "$3 " zfs_" $3}' > macrotable
  */
 
+#define	MEM_MODULE
+#define	XXH_NAMESPACE ZSTD_
+#define	XXH_PRIVATE_API
+#define	XXH_INLINE_ALL
+#define	ZSTD_LEGACY_SUPPORT 0
+#define	ZSTD_LIB_DICTBUILDER 0
+#define	ZSTD_LIB_DEPRECATED 0
+#define	ZSTD_NOBENCH
+#define	DEBUGLEVEL 0
+#ifdef _KERNEL
+#define	ZSTD_DEPS_ASSERT
+#endif
+
+
 #define	BIT_initDStream zfs_BIT_initDStream
 #define	BIT_mask zfs_BIT_mask
 #define	BIT_reloadDStream zfs_BIT_reloadDStream
@@ -406,7 +420,6 @@
 	zfs_ZSTD_insertAndFindFirstIndex_internal
 #define	ZSTD_insertBlock zfs_ZSTD_insertBlock
 #define	ZSTD_invalidateRepCodes zfs_ZSTD_invalidateRepCodes
-#define	ZSTD_isError zfs_ZSTD_isError
 #define	ZSTD_isFrame zfs_ZSTD_isFrame
 #define	ZSTD_ldm_adjustParameters zfs_ZSTD_ldm_adjustParameters
 #define	ZSTD_ldm_blockCompress zfs_ZSTD_ldm_blockCompress