Renames configure.in to fix warnings (#6034)

When building packages on ubuntu jammy, we started to see some warnings.

autoreconf: warning: autoconf input should be named 'configure.ac', not
'configure.in'

Makefile.global.in

@@ -64,8 +64,8 @@ $(citus_top_builddir)/Makefile.global: $(citus_abs_top_srcdir)/configure $(citus
 $(citus_top_builddir)/config.status: $(citus_abs_top_srcdir)/configure $(citus_abs_top_srcdir)/src/backend/distributed/citus.control
 	cd @abs_top_builddir@ && ./config.status --recheck && ./config.status
 
-# Regenerate configure if configure.in changed
-$(citus_abs_top_srcdir)/configure: $(citus_abs_top_srcdir)/configure.in
+# Regenerate configure if configure.ac changed
+$(citus_abs_top_srcdir)/configure: $(citus_abs_top_srcdir)/configure.ac
 	cd ${citus_abs_top_srcdir} && ./autogen.sh
 
 # If specified via configure, replace the default compiler. Normally

autogen.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# autogen.sh converts configure.in to configure and creates
+# autogen.sh converts configure.ac to configure and creates
 # citus_config.h.in. The resuting resulting files are checked into
 # the SCM, to avoid everyone needing autoconf installed.
 

config/general.m4

@@ -10,7 +10,7 @@
 # argument (other than "yes/no"), etc.
 #
 # The point of this implementation is to reduce code size and
-# redundancy in configure.in and to improve robustness and consistency
+# redundancy in configure.ac and to improve robustness and consistency
 # in the option evaluation code.
 
 

src/include/citus_config.h.in

@@ -1,4 +1,4 @@
-/* src/include/citus_config.h.in.  Generated from configure.in by autoheader.  */
+/* src/include/citus_config.h.in.  Generated from configure.ac by autoheader.  */
 
 
 /*