merge revision(s) 35ba2783,e8edc34f: [Backport #16807]

	Use a linked list to eliminate imemo tmp bufs for managing local
	 tables

	This patch changes local table memory to be managed by a linked list
	rather than via the garbage collector.  It reduces allocations from the
	GC and also fixes a use-after-free bug in the concurrent-with-sweep
	compactor I'm working on.

	Remove unused struct member

	I accidentally added this in 35ba2783,
	and it's making the size of RVALUE be too big. I'm sorry! orz