[1.2>master] [MERGE #979] FreeLoopBodyJobs race condition.
[1.2>master] [MERGE #979] FreeLoopBodyJobs race condition.

Merge pull request #979 from LouisLaf:stackjob
FreeLoopBodyJobs also need a processed flag to avoid race conditions.
To free data associated with a JIT loopbody, we create a FreeLoopBodyJob.  If we can't allocate one of these (OOM), we create one on the stack, and wait for it to be processed.
There was a race condition if we processed the job before starting to wait for it...  The 'processed' flag avoids this.

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