Add PathLike to genericpath.exists and re-export (#3897)

Closes#3492

stdlib/2/os2emxpath.pyi

@@ -5,6 +5,7 @@
 import os
 import sys
 from typing import overload, List, Any, AnyStr, Sequence, Tuple, TypeVar, Union, Text, Callable, Optional
+from genericpath import exists as exists
 
 _T = TypeVar('_T')
 
@@ -100,10 +101,6 @@ elif sys.version_info >= (3, 5):
 # So, fall back to Any
 def commonprefix(m: Sequence[_PathType]) -> Any: ...
 
-if sys.version_info >= (3, 3):
-    def exists(path: Union[_PathType, int]) -> bool: ...
-else:
-    def exists(path: _PathType) -> bool: ...
 def lexists(path: _PathType) -> bool: ...
 
 # These return float if os.stat_float_times() == True,