autotools: update the default for --with-unicode-version to 7.0.0

configure.ac

@@ -24,10 +24,10 @@ dnl UCD data configuration.
 dnl ================================================================
 
 AC_ARG_WITH([unicode-version],
-    [AS_HELP_STRING([--with-unicode-version], [Unicode version to support @<:@default=6.2.0@:>@])],
+    [AS_HELP_STRING([--with-unicode-version], [Unicode version to support @<:@default=7.0.0@:>@])],
     [AS_IF([test x"$withval" != x],
            [UCD_VERSION="$withval"])],
-    [UCD_VERSION="6.2.0"])
+    [UCD_VERSION="7.0.0"])
 
 AC_SUBST(UCD_VERSION)