Add CompressAsync and DecompressAsync

[brandonsturgeon]

Details

LZMA compression is very good, but it's also very slow.

Adding other algorithms seems like a pain, but it would be very nice if we had an asynchronous option.

Usage Example

local fileData = file.Read( "massiveFile.json", "DATA" )
util.CompressAsync( fileData, function( status/success, data )
    if not success or status ~= COMPRESS_SUCCESS then
        error( "Unable to compress data!" )
    end

    uploadData( data )
end )

Benchmark

Running util.Compress on a 35.77MB JSON Blob took 6.912s on a pretty powerful (4.8+ GHz) server. That means the server would have been fully locked up for almost 7 full seconds which is very not cool.

I know this isn't a great thing to do in Gmod, but it would sure be nice if we could without taking such a significant hit to performance.