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?

Misc/NEWS

@@ -38,7 +38,10 @@ Extension modules
 Library
 -------
 
-TBD
+- realpath is now exported when doing from poxixpath import *.
+  It is also exported for ntpath, macpath, and os2emxpath.
+  See SF bug #659228.
+
 
 Tools/Demos
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