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/code.pyi

@@ -0,0 +1,36 @@
+import sys
+from types import CodeType
+from typing import Any, Callable, Mapping, Optional
+
+class InteractiveInterpreter:
+    def __init__(self, locals: Optional[Mapping[str, Any]] = ...) -> None: ...
+    def runsource(self, source: str, filename: str = ..., symbol: str = ...) -> bool: ...
+    def runcode(self, code: CodeType) -> None: ...
+    def showsyntaxerror(self, filename: Optional[str] = ...) -> None: ...
+    def showtraceback(self) -> None: ...
+    def write(self, data: str) -> None: ...
+
+class InteractiveConsole(InteractiveInterpreter):
+    def __init__(self, locals: Optional[Mapping[str, Any]] = ..., filename: str = ...) -> None: ...
+    if sys.version_info >= (3, 6):
+        def interact(self, banner: Optional[str] = ..., exitmsg: Optional[str] = ...) -> None: ...
+    else:
+        def interact(self, banner: Optional[str] = ...) -> None: ...
+    def push(self, line: str) -> bool: ...
+    def resetbuffer(self) -> None: ...
+    def raw_input(self, prompt: str = ...) -> str: ...
+
+if sys.version_info >= (3, 6):
+    def interact(
+        banner: Optional[str] = ...,
+        readfunc: Optional[Callable[[str], str]] = ...,
+        local: Optional[Mapping[str, Any]] = ...,
+        exitmsg: Optional[str] = ...,
+    ) -> None: ...
+
+else:
+    def interact(
+        banner: Optional[str] = ..., readfunc: Optional[Callable[[str], str]] = ..., local: Optional[Mapping[str, Any]] = ...
+    ) -> None: ...
+
+def compile_command(source: str, filename: str = ..., symbol: str = ...) -> Optional[CodeType]: ...