Use correct OpenSSL thread safety macros on OS X (closes #209) Create an Autoconf test to determine if pthread_t is a pointer or scalar type, and use the appropriate CRYPTO_THREADID_set macro based on the result.

type t1 = {A : int, B : float}
type t2 = {B : float, A : int}
val e1 : t1 -> t2 = fn x => x