Update lingering configure.in references to say configure.ac

Doc/Manual/Extending.html

@@ -3101,7 +3101,7 @@ As you can see, most usages are direct.
 
 <dl>
 
-<dt> <b>configure.in</b>
+<dt> <b>configure.ac</b>
 <dd> This file is processed by
 
 <p>
@@ -3551,7 +3551,7 @@ details being outlined earlier on.
   a runtime test, see for example <tt>Examples/python/class</tt>.
   </li>
   <li>
-  Modify <tt>configure.in</tt>, <tt>Makefile.in</tt> and <tt>Examples/Makefile.in</tt> to run
+  Modify <tt>configure.ac</tt>, <tt>Makefile.in</tt> and <tt>Examples/Makefile.in</tt> to run
   these examples. Please make sure that if the new language is not
   installed properly on a box, <tt>make -k check</tt> should still work by
   skipping the tests and examples for the new language module.

Examples/php/check.list

@@ -1,5 +1,5 @@
 # see top-level Makefile.in
-# (see also top-level configure.in kludge)
+# (see also top-level configure.ac kludge)
 callback
 class
 constants

Makefile.in

@@ -514,11 +514,11 @@ configfiles:
 Makefile: $(srcdir)/Makefile.in config.status
 	$(SHELL) ./config.status
 
-# This target is usually called from Source/Makefile when configure.in has
+# This target is usually called from Source/Makefile when configure.ac has
 # changed.
 am--refresh: $(srcdir)/configure
 
-$(srcdir)/configure: $(srcdir)/configure.in
+$(srcdir)/configure: $(srcdir)/configure.ac
 	@echo "Build system is out of date.  If the following commands fail, please reconfigure by hand (rerun: ./autogen.sh && ./configure)"
 	cd $(srcdir) && ./autogen.sh
 	$(SHELL) ./config.status --recheck

configure.ac

@@ -2482,4 +2482,4 @@ AC_CONFIG_FILES([preinst-swig], [chmod +x preinst-swig])
 AC_CONFIG_FILES([CCache/ccache_swig_config.h])
 
 AC_OUTPUT
-dnl configure.in ends here
+dnl configure.ac ends here