Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/_random.pyi

@@ -0,0 +1,15 @@
+import sys
+from typing import Tuple
+
+# Actually Tuple[(int,) * 625]
+_State = Tuple[int, ...]
+
+class Random(object):
+    def __init__(self, seed: object = ...) -> None: ...
+    def seed(self, __n: object = ...) -> None: ...
+    def getstate(self) -> _State: ...
+    def setstate(self, __state: _State) -> None: ...
+    def random(self) -> float: ...
+    def getrandbits(self, __k: int) -> int: ...
+    if sys.version_info < (3,):
+        def jumpahead(self, i: int) -> None: ...