LZ4 magic number

[Vitch612]

I am not sure if this should be an issue or if it is intended behavior.
The lz4 frames produced by this extension do not have the expected lz4 magic number and are therefore incompatible with the lz4 software.

[r4m-alexd]

@Vitch612 Looks like this package uses common compression.
The magic number comes into play when you use streaming compression.

[cracksalad]

Interoperable versions of LZ4 must also respect the frame format.

from the lz4/lz4 README.md

I would appreciate frame format support as well.

In the mean time, I created a different PHP extension based on Rust, which does support frames as well as blocks (the format supported here).