Revert "Bug 983477 - Preserve scripts and the JIT code of PJS scripts across GCs for some maximum N GCs. (r=terrence,nmatsakis)"

This reverts commit 2951f04c4e2329253cfc99c15fea3eded1b64e43.
WIP -- Add preliminary vtune support
WIP -- Preallocate arenas before entering parallel execution
WIP -- Clear thread-local arenas after every iteration
WIP -- Improve bailout spew