Binary: Put -> Builder

[Chris Kuklewicz]

Don Stewart wrote:
> OK. I'm preparing the 0.5 release of binary atm, so will expose these.
> 
> -- Don

Don: I had proposed (with a patch) to let the caller of runPut give a size hint 
so the first chunk allocated for the Lazy ByteString would not have to always be 
the default value (which I remember being about 32 kilo bytes).  If the first 
allocation filled up the subsequent chunks are still the default size.

My use case was for the protocol-buffers package where the serialized message 
sizes are both known in advance and often much much smaller than this.  I have 
no benchmarks, but it feels wrong to have my library constantly over-allocating.

Is such a feature going to be accepted into the binary package?  If not then I 
may just copy over and patch the Put monad.  (I do not use an external Get 
monad, the protocol-buffers package includes its own Get monad).

Cheers,
    Chris