[Enhancement] Add option to encode in AdxVersion4 / Add Warning for AdxVersion4

[dreamsyntax]

Example Source File:

AdxHeader {
    encoding: Standard,
    block_size: 18,
    sample_bitdepth: 4,
    channel_count: 1,
    sample_rate: 24000,
    total_samples: 91968,
    highpass_frequency: 500,
    version: Version4,
    flags: 0
}

Output with encode -n

AdxHeader {
    encoding: Standard,
    block_size: 18,
    sample_bitdepth: 4,
    channel_count: 2,
    sample_rate: 24000,
    total_samples: 91968,
    highpass_frequency: 500,
    version: Version3(
        Some(
            AdxVersion3LoopInfo {
                alignment_samples: 0,
                enabled_short: 0,
                enabled_int: 0,
                begin_sample: 0,
                begin_byte: 0,
                end_sample: 0,
                end_byte: 0
            }
        )
    ),
    flags: 0
}

AdxVersion4 can be decoded just fine, encoding always returns to Version3.

Solution:

• Add ability to encode to AdxVersion3/4 with flag

I may open a PR if I get around to it.