Split stdlib into Python 2 and 3 versions (#5442)

All new files in stdlib/@python2 are straight copies of the
corresponding files in stdlib.

stdlib/@python2/smtpd.pyi

@@ -0,0 +1,96 @@
+import asynchat
+import asyncore
+import socket
+import sys
+from typing import Any, DefaultDict, List, Optional, Text, Tuple, Type, Union
+
+_Address = Tuple[str, int]  # (host, port)
+
+class SMTPChannel(asynchat.async_chat):
+    COMMAND: int
+    DATA: int
+
+    if sys.version_info >= (3,):
+        command_size_limits: DefaultDict[str, int]
+        smtp_server: SMTPServer
+        conn: socket.socket
+        addr: Any
+        received_lines: List[Text]
+        smtp_state: int
+        seen_greeting: str
+        mailfrom: str
+        rcpttos: List[str]
+        received_data: str
+        fqdn: str
+        peer: str
+
+        command_size_limit: int
+        data_size_limit: int
+
+        enable_SMTPUTF8: bool
+        @property
+        def max_command_size_limit(self) -> int: ...
+    if sys.version_info >= (3,):
+        def __init__(
+            self,
+            server: SMTPServer,
+            conn: socket.socket,
+            addr: Any,
+            data_size_limit: int = ...,
+            map: Optional[asyncore._maptype] = ...,
+            enable_SMTPUTF8: bool = ...,
+            decode_data: bool = ...,
+        ) -> None: ...
+    else:
+        def __init__(self, server: SMTPServer, conn: socket.socket, addr: Any, data_size_limit: int = ...) -> None: ...
+    # base asynchat.async_chat.push() accepts bytes
+    def push(self, msg: Text) -> None: ...  # type: ignore
+    def collect_incoming_data(self, data: bytes) -> None: ...
+    def found_terminator(self) -> None: ...
+    def smtp_HELO(self, arg: str) -> None: ...
+    def smtp_NOOP(self, arg: str) -> None: ...
+    def smtp_QUIT(self, arg: str) -> None: ...
+    def smtp_MAIL(self, arg: str) -> None: ...
+    def smtp_RCPT(self, arg: str) -> None: ...
+    def smtp_RSET(self, arg: str) -> None: ...
+    def smtp_DATA(self, arg: str) -> None: ...
+    if sys.version_info >= (3, 3):
+        def smtp_EHLO(self, arg: str) -> None: ...
+        def smtp_HELP(self, arg: str) -> None: ...
+        def smtp_VRFY(self, arg: str) -> None: ...
+        def smtp_EXPN(self, arg: str) -> None: ...
+
+class SMTPServer(asyncore.dispatcher):
+    channel_class: Type[SMTPChannel]
+
+    data_size_limit: int
+    enable_SMTPUTF8: bool
+
+    if sys.version_info >= (3,):
+        def __init__(
+            self,
+            localaddr: _Address,
+            remoteaddr: _Address,
+            data_size_limit: int = ...,
+            map: Optional[asyncore._maptype] = ...,
+            enable_SMTPUTF8: bool = ...,
+            decode_data: bool = ...,
+        ) -> None: ...
+    else:
+        def __init__(self, localaddr: _Address, remoteaddr: _Address, data_size_limit: int = ...) -> None: ...
+    def handle_accepted(self, conn: socket.socket, addr: Any) -> None: ...
+    def process_message(
+        self, peer: _Address, mailfrom: str, rcpttos: List[Text], data: Union[bytes, str], **kwargs: Any
+    ) -> Optional[str]: ...
+
+class DebuggingServer(SMTPServer): ...
+
+class PureProxy(SMTPServer):
+    def process_message(  # type: ignore
+        self, peer: _Address, mailfrom: str, rcpttos: List[Text], data: Union[bytes, str]
+    ) -> Optional[str]: ...
+
+class MailmanProxy(PureProxy):
+    def process_message(  # type: ignore
+        self, peer: _Address, mailfrom: str, rcpttos: List[Text], data: Union[bytes, str]
+    ) -> Optional[str]: ...