context_unify3 branch is (almost) ready to merge back to trunk.

[Vasily Chekalkin]

Hello.

(Just in case if someone will able to hack on this branch for next ~12 
hours.)

To simplify life of HLL developers I'm going to do next things:

1. Implement new function Parrot_pcc_(get|set)_next_call_context (or 
similar with better name) which will be accessor to 
"interp->current_sig". It will be used in "build_sigobject", 
"invoke_from_sigobject" and various "op invoke".
2. Switch Parrot_pcc_get_signature to return current context.

Main reason is - HLL devs depends on getting current "CallSignature" 
from CURRENT_CONTEXT using Parrot_pcc_get_signature. PCC depends on 
building CallContext on same functions. But PCC builds signature for 
future use, HLL - for current use. So, it's better to use different 
accessors.

-- 
Bacek,
falling asleep at face of future.