Enums should be considered Trivial types in Atomics

[mratsim]

Enums are int16 sized at most and should be trivial types in Atomics.

Nim/lib/pure/concurrency/atomics.nim

Lines 136 to 139 in de1a283

	type
	Trivial = SomeNumber | bool | ptr | pointer
	# A type that is known to be atomic and whose size is known at
	# compile time to be 8 bytes or less