added -Wpointer-arith and -Wchar-subscripts

diff --git a/configure.in b/configure.in
index 0c3e8dd..da0cad6 100644
--- a/configure.in
+++ b/configure.in
@@ -61,9 +61,10 @@
    CFLAGS="$CFLAGS -Wshadow"
    CFLAGS="$CFLAGS -Wcast-qual"
    CFLAGS="$CFLAGS -Wcast-align"
+   CFLAGS="$CFLAGS -Wpointer-arith"
+   CFLAGS="$CFLAGS -Wchar-subscripts"
    CFLAGS="$CFLAGS -Wmissing-prototypes"
    CFLAGS="$CFLAGS -Wmissing-declarations"
-   CFLAGS="$CFLAGS -Wredundant-decls"
    ;;
 esac