bpo-38109: Add missing constants to Lib/stat.py (GH-16665)

Add missing stat.S_IFDOOR, stat.S_IFPORT, stat.S_IFWHT,
stat.S_ISDOOR, stat.S_ISPORT, and stat.S_ISWHT values to
the Python implementation of the stat module.

Lib/stat.py

@@ -40,6 +40,10 @@ S_IFREG  = 0o100000  # regular file
 S_IFIFO  = 0o010000  # fifo (named pipe)
 S_IFLNK  = 0o120000  # symbolic link
 S_IFSOCK = 0o140000  # socket file
+# Fallbacks for uncommon platform-specific constants
+S_IFDOOR = 0
+S_IFPORT = 0
+S_IFWHT = 0
 
 # Functions to test for each file type
 
@@ -71,6 +75,18 @@ def S_ISSOCK(mode):
     """Return True if mode is from a socket."""
     return S_IFMT(mode) == S_IFSOCK
 
+def S_ISDOOR(mode):
+    """Return True if mode is from a door."""
+    return False
+
+def S_ISPORT(mode):
+    """Return True if mode is from an event port."""
+    return False
+
+def S_ISWHT(mode):
+    """Return True if mode is from a whiteout."""
+    return False
+
 # Names for permission bits
 
 S_ISUID = 0o4000  # set UID bit