expose make_optional to cython

Summary: This definition is the same cython uses for make_shared and make_unique

Reviewed By: yfeldblum

Differential Revision: D30232407

fbshipit-source-id: 6a0cf4637721bc9d5e5f7f87f3c0f2b031810a5f

folly/python/optional.pxd

@@ -22,3 +22,5 @@ cdef extern from "folly/Optional.h" namespace "folly" nogil:
         T* get_pointer()
         void reset()
         void assign(T&& newValue)
+
+    cOptional[T] make_optional[T](...) except +