Added rule to automatically run autoconf & config.status whenever configure.in changes. Set AUTOUPDATE_CONFIGURE to use it.

config/autoconf.mk.in

@@ -162,6 +162,7 @@ TARGET_CPU	= @TARGET_CPU@
 TARGET_OS	= @TARGET_OS@
 TARGET_MD_ARCH	= @TARGET_MD_ARCH@
 
+AUTOCONF	= @AUTOCONF@
 EMACS		= @EMACS@
 PERL		= @PERL@
 RANLIB		= @RANLIB@

config/rules.mk

@@ -838,7 +838,7 @@ endif #STRICT_CPLUSPLUS_SUFFIX
 ###############################################################################
 # Note: Passing depth to make-makefile is optional.
 #       It saves the script some work, though.
-Makefile: Makefile.in
+Makefile: Makefile.in $(topsrcdir)/configure
 	@$(PERL) $(AUTOCONF_TOOLS)/make-makefile -t $(topsrcdir) -d $(DEPTH) 
 
 ifdef SUBMAKEFILES
@@ -847,6 +847,11 @@ $(SUBMAKEFILES): % : $(srcdir)/%.in
 	@$(PERL) $(AUTOCONF_TOOLS)/make-makefile -t $(topsrcdir) -d $(DEPTH) $@
 endif
 
+ifdef AUTOUPDATE_CONFIGURE
+$(topsrcdir)/configure: $(topsrcdir)/configure.in
+	(cd $(topsrcdir) && $(AUTOCONF)) && (cd $(DEPTH) && ./config.status --recheck)
+endif
+
 ###############################################################################
 # Bunch of things that extend the 'export' rule (in order):
 ###############################################################################