(Merge 3.3) fileutils.c: use MAXPATHLEN instead of PATH_MAX

PATH_MAX is not declared on IRIX nor Windows.
diff --git a/Python/fileutils.c b/Python/fileutils.c
index b504b15..814f076 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -869,7 +869,7 @@
 _Py_wreadlink(const wchar_t *path, wchar_t *buf, size_t bufsiz)
 {
     char *cpath;
-    char cbuf[PATH_MAX];
+    char cbuf[MAXPATHLEN];
     wchar_t *wbuf;
     int res;
     size_t r1;
@@ -879,11 +879,11 @@
         errno = EINVAL;
         return -1;
     }
-    res = (int)readlink(cpath, cbuf, PATH_MAX);
+    res = (int)readlink(cpath, cbuf, Py_ARRAY_LENGTH(cbuf));
     PyMem_Free(cpath);
     if (res == -1)
         return -1;
-    if (res == PATH_MAX) {
+    if (res == Py_ARRAY_LENGTH(cbuf)) {
         errno = EINVAL;
         return -1;
     }
@@ -915,7 +915,7 @@
               wchar_t *resolved_path, size_t resolved_path_size)
 {
     char *cpath;
-    char cresolved_path[PATH_MAX];
+    char cresolved_path[MAXPATHLEN];
     wchar_t *wresolved_path;
     char *res;
     size_t r;
@@ -956,11 +956,11 @@
     int isize = (int)Py_MIN(size, INT_MAX);
     return _wgetcwd(buf, isize);
 #else
-    char fname[PATH_MAX];
+    char fname[MAXPATHLEN];
     wchar_t *wname;
     size_t len;
 
-    if (getcwd(fname, PATH_MAX) == NULL)
+    if (getcwd(fname, Py_ARRAY_LENGTH(fname)) == NULL)
         return NULL;
     wname = _Py_char2wchar(fname, &len);
     if (wname == NULL)