Request for reviews (M): 6684714: Optimize EA Connection Graph build performance

[Vladimir Kozlov]

http://webrev.invokedynamic.info/kvn/6684714/index.html

Fixed 6684714: Optimize EA Connection Graph build performance

Problem:
EA spends most time in Connection Graph construction which is done
during each method compilation since only after CG built it can
look for scalar replaceable candidates and create unique types
for fields instances or skip it if there are no such candidates.
Especially it is critical for [fast]debug VM which spends about
30% of the compilation time in Connection Graph construction.

Solution:
1. Build Connection Graph and execute Escape Analysis only
when Ideal graph has allocations.
2. Replace growable arrays and vector sets with arena arrays
where possible (their size is fixed since Connection Graph
construction doesn't add Ideal nodes).
3. Optimize ConnectionGraph::remove_derefered() and PointsTo()
most expensive methods.

Connection Graph build performance improved by x3 in debug VM.

Reviewed by:
Fix verified (y/n): y

Other testing:
JPRT, CTW, NSK