Add lock_on parameter in SASIndexSpillAlloc and SASIndexSpillAllocExtended

	* src/sasindex.cpp (SASIndexSpillAlloc): Add lock_on_t parm.
	Conditionally call SASLock/SASUnlock.
	(SASIndexSpillAllocExtended): Add lock_on_t parm.
	Conditionally call SASLock/SASUnlock.
	* src/sasindex.h: Minor comment change.
	* src/sasindexenum.cpp: Update debug statements to print lock_on.
	* src/sasindexnode.cpp: Update debug statements to print lock_on.
	(SASIndexNodeNearAlloc): Pass lock_on to SASIndexSpillAlloc().
	* src/sasindexpriv.h (SASIndexSpillAlloc): Add lock_on_t parm.