r8252: Steal metze's thunder, and prove that with a few small tweaks, we can

r8252: Steal metze's thunder, and prove that with a few small tweaks, we can
now push/pull a sample PAC, and still have the same byte buffer.
(Metze set up the string code, and probably already has a similar
patch).

Unfortunetly win2k3 still doesn't like what we provide, but every step helps.

Also use data_blob_const() when we are just wrapping data for API
reasons.

Andrew Bartlett