Decoder: allow to specify the buffer size

[ngirard]

Hey,

while tweaking the encoder's parameters for my Lolcate program, I experienced a performance increase when increasing its block size (I found a sweet spot at 256 kb).

This made me willing to try and give the decoder's buffer size different values, hoping to get similar performance increases, given that the default value seems small.

Is there any interest in doing so, or is the default value the best one in your own experience ?

Cheers