Summary: collection of small changes to prepare for incremental inlining.
Reviewed-by: twisti, kvn

Reviewed-by: kvn, twisti
Contributed-by: NBharadwaj Yadavalli <bharadwaj.yadavalli@oracle.com>

Reviewed-by: jrose, kvn

Summary: Move the handelization of 'last' to a point before the GC might enter.
Reviewed-by: dholmes, sspitsyn, coleenp

Summary: use unsigned comparison when checking for stack overflow
Reviewed-by: kvn, twisti
Contributed-by: paul.nauman@oracle.com

Summary: fixed build failure for Zero target
Reviewed-by: twisti, kvn

Reviewed-by: jcoomes