PPC: VectorICs: allocating slots for store ics in ast nodes.

Port 5450fc07

Original commit message:
Also adapt code generation to pass the slot to the
store/keyed-store ic. AST nodes ObjectLiteral, Assignment,
ForEach, Call and CountOperation now include one or more
feedback vector ic slot ids.

R=mvstanton@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1156503003

Cr-Commit-Position: refs/heads/master@{#28666}