Fix SF #659228, 'realpath' function missing from os.path

Also added realpath = abspath for os2emx, similar to windows/mac
which also don't really implement realpath.

Backport candidate, I think?

Lib/macpath.py

@@ -7,7 +7,7 @@ __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
            "getatime","getctime", "islink","exists","isdir","isfile",
            "walk","expanduser","expandvars","normpath","abspath",
-           "supports_unicode_filenames"]
+           "realpath","supports_unicode_filenames"]
 
 # Normalize the case of a pathname.  Dummy in Posix, but <s>.lower() here.
 

Lib/ntpath.py

@@ -13,7 +13,7 @@ __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
            "getatime","getctime", "islink","exists","isdir","isfile","ismount",
            "walk","expanduser","expandvars","normpath","abspath","splitunc",
-           "supports_unicode_filenames"]
+           "realpath","supports_unicode_filenames"]
 
 # Normalize the case of a pathname and map slashes to backslashes.
 # Other normalizations (such as optimizing '../' away) are not done

Lib/os2emxpath.py

@@ -12,7 +12,7 @@ __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
            "getatime","getctime", "islink","exists","isdir","isfile","ismount",
            "walk","expanduser","expandvars","normpath","abspath","splitunc",
-           "supports_unicode_filenames"]
+           "realpath","supports_unicode_filenames"]
 
 # Normalize the case of a pathname and map slashes to backslashes.
 # Other normalizations (such as optimizing '../' away) are not done
@@ -405,4 +405,7 @@ def abspath(path):
         path = join(os.getcwd(), path)
     return normpath(path)
 
+# realpath is a no-op on systems without islink support
+realpath = abspath
+
 supports_unicode_filenames = False

Lib/posixpath.py

@@ -17,7 +17,8 @@ __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
            "getatime","getctime","islink","exists","isdir","isfile","ismount",
            "walk","expanduser","expandvars","normpath","abspath",
-           "samefile","sameopenfile","samestat","supports_unicode_filenames"]
+           "samefile","sameopenfile","samestat",
+           "realpath","supports_unicode_filenames"]
 
 # Normalize the case of a pathname.  Trivial in Posix, string.lower on Mac.
 # On MS-DOS this may also turn slashes into backslashes; however, other