Define MAXPATHLEN to be at least PATH_MAX, if that's defined. Python uses

MAXPATHLEN-sized buffers for various output-buffers (like to realpath()),
and that's correct on BSD platforms, but not Linux (which uses PATH_MAX, and
does not define MAXPATHLEN.) Cursory googling suggests Linux is following a
newer standard than BSD, but in cases like this, who knows. Using the
greater of PATH_MAX and 1024 as a fallback for MAXPATHLEN seems to be the
most portable solution.

Modules/posixmodule.c

@@ -262,7 +262,11 @@ extern int lstat(const char *, struct stat *);
 #endif /* OS2 */
 
 #ifndef MAXPATHLEN
+#if defined(PATH_MAX) && PATH_MAX > 1024
+#define MAXPATHLEN PATH_MAX
+#else
 #define MAXPATHLEN 1024
+#endif
 #endif /* MAXPATHLEN */
 
 #ifdef UNION_WAIT