zstd: x86 assembler implementation of sequenceDecs.decode (#528)

* zstd: x86 assembler implementation of sequenceDecs.decode

Differences with the Go implementation:
- check ml and mo in the main loop,
- s.seqSize and litRemain are checked in the end.

Generate assembly routines with avo

Author: WojciechMula

.gitignore

@@ -23,3 +23,10 @@ _testmain.go
 *.test
 *.prof
 /s2/cmd/_s2sx/sfx-exe
+
+# Linux perf files
+perf.data
+perf.data.old
+
+# gdb history
+.gdb_history