LZ4 decompressor stop upon detect other SKIPPABLE frame! These frames should be ignored.

[remittor]

https://github.com/lz4/lz4/blob/dev/doc/lz4_Frame_format.md#skippable-frames

4 Bytes, Little endian format. Value : 0x184D2A5X, which means any value from 0x184D2A50 to 0x184D2A5F. All 16 values are valid to identify a skippable frame.

Because of this, the 7zip-Zstd will only unpack its own archives.

Using mutexes only slows down LZ4 packer!!!

[mcmilk]

Please don't use a ot of "!!!" - it's not nice.

I also think, that the code skips the skippable... if not, that would be really a bug in zstdmt code.

[mcmilk]

Hello remittor, can you give some example for the bad behavior of zstdmt... if yes, then please re-open that issue here.