(from IBM TopPage patch) return correct error for already existing
file.

files/file.c

diff --git a/files/file.c b/files/file.c
index e85f4b3..1252f0b 100644
--- a/files/file.c
+++ b/files/file.c
@@ -1762,9 +1762,11 @@
     TRACE("(%s,%s)\n", fn1, fn2 );
 
     if (!DOSFS_GetFullName( fn1, TRUE, &full_name1 )) return FALSE;
-    if (DOSFS_GetFullName( fn2, TRUE, &full_name2 )) 
+    if (DOSFS_GetFullName( fn2, TRUE, &full_name2 ))  {
       /* The new name must not already exist */ 
+      SetLastError(ERROR_ALREADY_EXISTS);
       return FALSE;
+    }
     if (!DOSFS_GetFullName( fn2, FALSE, &full_name2 )) return FALSE;
 
     if (full_name1.drive == full_name2.drive) /* move */