Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/shlex.pyi

@@ -0,0 +1,45 @@
+import sys
+from typing import Any, Iterable, List, Optional, TextIO, Tuple, TypeVar, Union
+
+def split(s: str, comments: bool = ..., posix: bool = ...) -> List[str]: ...
+
+if sys.version_info >= (3, 8):
+    def join(split_command: Iterable[str]) -> str: ...
+
+def quote(s: str) -> str: ...
+
+_SLT = TypeVar("_SLT", bound=shlex)
+
+class shlex(Iterable[str]):
+    commenters: str
+    wordchars: str
+    whitespace: str
+    escape: str
+    quotes: str
+    escapedquotes: str
+    whitespace_split: bool
+    infile: str
+    instream: TextIO
+    source: str
+    debug: int
+    lineno: int
+    token: str
+    eof: str
+    punctuation_chars: str
+    def __init__(
+        self,
+        instream: Union[str, TextIO] = ...,
+        infile: Optional[str] = ...,
+        posix: bool = ...,
+        punctuation_chars: Union[bool, str] = ...,
+    ) -> None: ...
+    def get_token(self) -> str: ...
+    def push_token(self, tok: str) -> None: ...
+    def read_token(self) -> str: ...
+    def sourcehook(self, filename: str) -> Tuple[str, TextIO]: ...
+    # TODO argument types
+    def push_source(self, newstream: Any, newfile: Any = ...) -> None: ...
+    def pop_source(self) -> None: ...
+    def error_leader(self, infile: str = ..., lineno: int = ...) -> None: ...
+    def __iter__(self: _SLT) -> _SLT: ...
+    def __next__(self) -> str: ...