Fix autotools warnings

Makefile.am

@@ -1,5 +1,5 @@
 ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS}
-INCLUDES = src
+AM_CPPFLAGS = src
 
 SUBDIRS = \
 	src	\

configure.ac

@@ -1,6 +1,6 @@
 AC_INIT([Zenity],[3.30.0],[https://bugzilla.gnome.org/enter_bug.cgi?product=zenity],[zenity])
 
-AC_PREREQ([2.63])
+AC_PREREQ([2.69])
 
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_SRCDIR([src])
@@ -11,6 +11,12 @@ AM_MAINTAINER_MODE([enable])
 
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
 
+# *******************************
+# Debug
+# *******************************
+
+AX_CHECK_ENABLE_DEBUG([yes],[GNOME_ENABLE_DEBUG])
+
 # Check for programs
 AC_PROG_CC
 
@@ -27,7 +33,7 @@ dnl *************************
 zenity_save_cflags="$CFLAGS"
 # pull in the CFLAGS to locate gdkconfig.h
 CFLAGS=`$PKG_CONFIG --cflags gtk+-3.0`
-AC_COMPILE_IFELSE([
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
 #include <gdk/gdk.h>
 
 int main(void) {
@@ -36,7 +42,7 @@ int main(void) {
 #endif
     return 0;
 }
-],
+])],
         GDK_BACKEND_X11=yes,
         GDK_BACKEND_X11=no)
 
@@ -98,12 +104,6 @@ if test x$enable_webkitgtk = xyes; then
         fi
 fi
 
-# *******************************
-# Debug
-# ******************************* 
-
-AX_CHECK_ENABLE_DEBUG([yes],[GNOME_ENABLE_DEBUG])
-
 
 # *******************************
 # Internationalization