Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/@python2/imp.pyi

@@ -0,0 +1,33 @@
+import types
+from typing import IO, Any, Iterable, List, Optional, Tuple
+
+C_BUILTIN: int
+C_EXTENSION: int
+IMP_HOOK: int
+PKG_DIRECTORY: int
+PY_CODERESOURCE: int
+PY_COMPILED: int
+PY_FROZEN: int
+PY_RESOURCE: int
+PY_SOURCE: int
+SEARCH_ERROR: int
+
+def acquire_lock() -> None: ...
+def find_module(name: str, path: Iterable[str] = ...) -> Optional[Tuple[IO[Any], str, Tuple[str, str, int]]]: ...
+def get_magic() -> str: ...
+def get_suffixes() -> List[Tuple[str, str, int]]: ...
+def init_builtin(name: str) -> types.ModuleType: ...
+def init_frozen(name: str) -> types.ModuleType: ...
+def is_builtin(name: str) -> int: ...
+def is_frozen(name: str) -> bool: ...
+def load_compiled(name: str, pathname: str, file: IO[Any] = ...) -> types.ModuleType: ...
+def load_dynamic(name: str, pathname: str, file: IO[Any] = ...) -> types.ModuleType: ...
+def load_module(name: str, file: str, pathname: str, description: Tuple[str, str, int]) -> types.ModuleType: ...
+def load_source(name: str, pathname: str, file: IO[Any] = ...) -> types.ModuleType: ...
+def lock_held() -> bool: ...
+def new_module(name: str) -> types.ModuleType: ...
+def release_lock() -> None: ...
+
+class NullImporter:
+    def __init__(self, path_string: str) -> None: ...
+    def find_module(self, fullname: str, path: str = ...) -> None: ...