Clean up library function spawning in base analysis

[sim642]

Since #1029 is now done, it should be possible to clean up this TODO:

analyzer/src/analyses/base.ml

Lines 2169 to 2173 in 3ad6b39

	| _, _ when get_bool "sem.unknown_function.spawn" ->
	(* TODO: Remove sem.unknown_function.spawn check because it is (and should be) really done in LibraryFunctions.
	But here we consider all non-ThreadCreate functions also unknown, so old-style LibraryFunctions access
	definitions using `Write would still spawn because they are not truly unknown functions (missing from LibraryFunctions).
	Need this to not have memmove spawn in SV-COMP. *)