- rename configure.in to configure.ac
- change references from configure.in to configure.ac
diff --git a/Include/patchlevel.h b/Include/patchlevel.h
index 9fc6e97..7f62cdb 100644
--- a/Include/patchlevel.h
+++ b/Include/patchlevel.h
@@ -2,7 +2,7 @@
 /* Python version identification scheme.
 
    When the major or minor version changes, the VERSION variable in
-   configure.in must also be changed.
+   configure.ac must also be changed.
 
    There is also (independent) API version information in modsupport.h.
 */