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/macpath.pyi

@@ -0,0 +1,104 @@
+import sys
+from _typeshed import AnyPath, BytesPath, StrPath
+from genericpath import (
+    commonprefix as commonprefix,
+    exists as exists,
+    getatime as getatime,
+    getctime as getctime,
+    getmtime as getmtime,
+    getsize as getsize,
+    isdir as isdir,
+    isfile as isfile,
+)
+
+if sys.version_info >= (3, 4):
+    from genericpath import samefile as samefile, sameopenfile as sameopenfile, samestat as samestat
+
+# Re-export common definitions from posixpath to reduce duplication
+from posixpath import (
+    abspath as abspath,
+    curdir as curdir,
+    defpath as defpath,
+    devnull as devnull,
+    expanduser as expanduser,
+    expandvars as expandvars,
+    extsep as extsep,
+    isabs as isabs,
+    lexists as lexists,
+    pardir as pardir,
+    pathsep as pathsep,
+    sep as sep,
+    splitdrive as splitdrive,
+    splitext as splitext,
+    supports_unicode_filenames as supports_unicode_filenames,
+)
+from typing import AnyStr, Optional, Text, Tuple, overload
+
+altsep: Optional[str]
+
+if sys.version_info >= (3, 6):
+    from os import PathLike
+    @overload
+    def basename(s: PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def basename(s: AnyStr) -> AnyStr: ...
+    @overload
+    def dirname(s: PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def dirname(s: AnyStr) -> AnyStr: ...
+    @overload
+    def normcase(path: PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def normcase(path: AnyStr) -> AnyStr: ...
+    @overload
+    def normpath(s: PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def normpath(s: AnyStr) -> AnyStr: ...
+    @overload
+    def realpath(path: PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def realpath(path: AnyStr) -> AnyStr: ...
+
+else:
+    def basename(s: AnyStr) -> AnyStr: ...
+    def dirname(s: AnyStr) -> AnyStr: ...
+    def normcase(path: AnyStr) -> AnyStr: ...
+    def normpath(s: AnyStr) -> AnyStr: ...
+    def realpath(path: AnyStr) -> AnyStr: ...
+
+def islink(s: AnyPath) -> bool: ...
+
+if sys.version_info >= (3, 6):
+    # Mypy complains that the signatures overlap, but things seem to behave correctly anyway.
+    @overload
+    def join(s: StrPath, *paths: StrPath) -> Text: ...
+    @overload
+    def join(s: BytesPath, *paths: BytesPath) -> bytes: ...
+
+elif sys.version_info >= (3, 0):
+    def join(s: AnyStr, *paths: AnyStr) -> AnyStr: ...
+
+else:
+    # Make sure signatures are disjunct, and allow combinations of bytes and unicode.
+    # (Since Python 2 allows that, too)
+    # Note that e.g. os.path.join("a", "b", "c", "d", u"e") will still result in
+    # a type error.
+    @overload
+    def join(__p1: bytes, *p: bytes) -> bytes: ...
+    @overload
+    def join(__p1: bytes, __p2: bytes, __p3: bytes, __p4: Text, *p: AnyPath) -> Text: ...
+    @overload
+    def join(__p1: bytes, __p2: bytes, __p3: Text, *p: AnyPath) -> Text: ...
+    @overload
+    def join(__p1: bytes, __p2: Text, *p: AnyPath) -> Text: ...
+    @overload
+    def join(__p1: Text, *p: AnyPath) -> Text: ...
+
+if sys.version_info >= (3, 6):
+    @overload
+    def split(s: PathLike[AnyStr]) -> Tuple[AnyStr, AnyStr]: ...
+    @overload
+    def split(s: AnyStr) -> Tuple[AnyStr, AnyStr]: ...
+
+else:
+    def split(s: AnyStr) -> Tuple[AnyStr, AnyStr]: ...