Added directfs

Added a very rudimentary file I/O system suitable for experimenting
with the language further. A better one will be designed when we have
sensible error management.

src/systems/stl/tuple.orc

@@ -0,0 +1,16 @@
+import super::(known::*, bool::*, num::*)
+
+const discard_args := \n.\value. (
+  if n == 0 then value
+  else \_. discard_args (n - 1) value
+)
+
+export const pick := \tuple. \i.\n. tuple (
+  discard_args i \val. discard_args (n - 1 - i) val
+)
+
+macro t[...$item, ...$rest:1] =0x2p84=> (\f. t[...$rest] (f (...$item)))
+macro t[...$end] =0x1p84=> (\f. f (...$end))
+macro t[] =0x1p84=> \f.f
+
+export ::(t)