More fixes related to PathLike (#1061)

* Make DirEntry generic over AnyStr, and inherit from PathLike if it exists

* Make pathlib require PathLike[str] (when it exists)

stdlib/3/os/__init__.pyi

@@ -118,13 +118,27 @@ if sys.version_info >= (3, 6):
 
 _PathType = Union[bytes, Text]
 
-if sys.version_info >= (3, 5):
-    class DirEntry:
+if sys.version_info >= (3, 6):
+    class DirEntry(PathLike[AnyStr]):
         # This is what the scandir interator yields
         # The constructor is hidden
 
-        name = ''
-        path = ''
+        name = ...  # type: AnyStr
+        path = ...  # type: AnyStr
+        def inode(self) -> int: ...
+        def is_dir(self, follow_symlinks: bool = ...) -> bool: ...
+        def is_file(self, follow_symlinks: bool = ...) -> bool: ...
+        def is_symlink(self) -> bool: ...
+        def stat(self) -> stat_result: ...
+
+        def __fspath__(self) -> AnyStr: ...
+elif sys.version_info >= (3, 5):
+    class DirEntry(Generic[AnyStr]):
+        # This is what the scandir interator yields
+        # The constructor is hidden
+
+        name = ...  # type: AnyStr
+        path = ...  # type: AnyStr
         def inode(self) -> int: ...
         def is_dir(self, follow_symlinks: bool = ...) -> bool: ...
         def is_file(self, follow_symlinks: bool = ...) -> bool: ...
@@ -308,9 +322,9 @@ if sys.version_info >= (3, 3):
 def rmdir(path: _PathType) -> None: ...
 if sys.version_info >= (3, 5):
     @overload
-    def scandir(path: str = ...) -> Iterator[DirEntry]: ...
+    def scandir(path: str = ...) -> Iterator[DirEntry[str]]: ...
     @overload
-    def scandir(path: bytes) -> Iterator[DirEntry]: ...
+    def scandir(path: bytes) -> Iterator[DirEntry[bytes]]: ...
 def stat(path: _PathType) -> stat_result: ...
 def stat_float_times(newvalue: Union[bool, None] = ...) -> bool: ...
 def statvfs(path: _PathType) -> statvfs_result: ...  # Unix only