Replace macros deprecated in automake-1.13; fixed upstream in glib-2.36

diff --git a/configure.ac b/configure.ac
index a3567b3..3e3d697 100644
--- a/configure.ac
+++ b/configure.ac
@@ -56,7 +56,7 @@ m4_define([glib_debug_default],
 AC_INIT(glib, [glib_version],
         [http://bugzilla.gnome.org/enter_bug.cgi?product=glib])
 
-AC_CONFIG_HEADER([config.h])
+AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_SRCDIR([glib/glib.h])
 AC_CONFIG_MACRO_DIR([m4macros])
 
@@ -291,7 +291,6 @@ AC_TRY_COMPILE(,[class a { int b; } c;], ,CXX=)
 AM_CONDITIONAL(HAVE_CXX, [test "$CXX" != ""])
 AC_LANG_RESTORE
 
-AM_PROG_CC_STDC
 AM_PROG_CC_C_O
 AC_PROG_INSTALL