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/dis.pyi

@@ -0,0 +1,83 @@
+import sys
+import types
+from opcode import (
+    EXTENDED_ARG as EXTENDED_ARG,
+    HAVE_ARGUMENT as HAVE_ARGUMENT,
+    cmp_op as cmp_op,
+    hascompare as hascompare,
+    hasconst as hasconst,
+    hasfree as hasfree,
+    hasjabs as hasjabs,
+    hasjrel as hasjrel,
+    haslocal as haslocal,
+    hasname as hasname,
+    opmap as opmap,
+    opname as opname,
+)
+from typing import IO, Any, Callable, Dict, Iterator, List, NamedTuple, Optional, Tuple, Union
+
+if sys.version_info >= (3, 4):
+    from opcode import stack_effect as stack_effect
+
+if sys.version_info >= (3, 6):
+    from opcode import hasnargs as hasnargs
+
+# Strictly this should not have to include Callable, but mypy doesn't use FunctionType
+# for functions (python/mypy#3171)
+_have_code = Union[types.MethodType, types.FunctionType, types.CodeType, type, Callable[..., Any]]
+_have_code_or_string = Union[_have_code, str, bytes]
+
+if sys.version_info >= (3, 4):
+    class Instruction(NamedTuple):
+        opname: str
+        opcode: int
+        arg: Optional[int]
+        argval: Any
+        argrepr: str
+        offset: int
+        starts_line: Optional[int]
+        is_jump_target: bool
+    class Bytecode:
+        codeobj: types.CodeType
+        first_line: int
+        def __init__(
+            self, x: _have_code_or_string, *, first_line: Optional[int] = ..., current_offset: Optional[int] = ...
+        ) -> None: ...
+        def __iter__(self) -> Iterator[Instruction]: ...
+        def __repr__(self) -> str: ...
+        def info(self) -> str: ...
+        def dis(self) -> str: ...
+        @classmethod
+        def from_traceback(cls, tb: types.TracebackType) -> Bytecode: ...
+
+COMPILER_FLAG_NAMES: Dict[int, str]
+
+def findlabels(code: _have_code) -> List[int]: ...
+def findlinestarts(code: _have_code) -> Iterator[Tuple[int, int]]: ...
+
+if sys.version_info >= (3, 0):
+    def pretty_flags(flags: int) -> str: ...
+    def code_info(x: _have_code_or_string) -> str: ...
+
+if sys.version_info >= (3, 7):
+    def dis(x: Optional[_have_code_or_string] = ..., *, file: Optional[IO[str]] = ..., depth: Optional[int] = ...) -> None: ...
+
+elif sys.version_info >= (3, 4):
+    def dis(x: Optional[_have_code_or_string] = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+
+else:
+    def dis(x: _have_code_or_string = ...) -> None: ...
+
+if sys.version_info >= (3, 4):
+    def distb(tb: Optional[types.TracebackType] = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def disassemble(co: _have_code, lasti: int = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def disco(co: _have_code, lasti: int = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def show_code(co: _have_code, *, file: Optional[IO[str]] = ...) -> None: ...
+    def get_instructions(x: _have_code, *, first_line: Optional[int] = ...) -> Iterator[Instruction]: ...
+
+else:
+    def distb(tb: types.TracebackType = ...) -> None: ...
+    def disassemble(co: _have_code, lasti: int = ...) -> None: ...
+    def disco(co: _have_code, lasti: int = ...) -> None: ...
+    if sys.version_info >= (3, 0):
+        def show_code(co: _have_code) -> None: ...