gc_encapsulate_part_2

[Vasily Chekalkin]

Hello.

Branch is ready for _extensive_ testing. Especially with HLLs.

Main purpose of branch: encapsulate all access to interp->mem_pools 
inside gc_ms.


Some statistic:
bacek at icering:~/src/parrot$ ack -clQ 'interp->mem' src
src/gc/gc_ms.c:63

Branch probably introduced some slowing down due indirect function call. 
But we can reuse same tactic with macros as in Context API.

So, testing, documentation updates and general cheer-up welcome :)

-- 
Bacek