Ship UCDN and use it by default

So we are not relying on version of Unicode data in glib...

Fixes https://github.com/behdad/harfbuzz/issues/386
Fixes https://github.com/behdad/harfbuzz/issues/388

configure.ac

@@ -289,9 +289,13 @@ AM_CONDITIONAL(HAVE_ICU_BUILTIN, $have_icu && test "x$with_icu" = "xbuiltin")
 
 dnl ===========================================================================
 
-have_ucdn=true
-if $have_glib || test \( $have_icu -a "x$with_icu" = "xbuiltin" \); then
-	have_ucdn=false
+AC_ARG_WITH(ucdn,
+	[AS_HELP_STRING([--with-ucdn=@<:@yes/no@:>@],
+			[Use builtin UCDN library @<:@default=yes@:>@])],,
+	[with_ucdn=yes])
+have_ucdn=false
+if test "x$with_ucdn" = "xyes"; then
+	have_ucdn=true
 fi
 if $have_ucdn; then
 	AC_DEFINE(HAVE_UCDN, 1, [Have UCDN Unicode functions])
@@ -501,9 +505,9 @@ AC_MSG_NOTICE([
 Build configuration:
 
 Unicode callbacks (you want at least one):
+	Builtin (UCDN):		${have_ucdn}
 	Glib:			${have_glib}
 	ICU:			${have_icu}
-	UCDN:			${have_ucdn}
 
 Font callbacks (the more the better):
 	FreeType:		${have_freetype}

src/hb-unicode.cc

@@ -131,12 +131,12 @@ hb_unicode_funcs_get_default (void)
 #define HB_UNICODE_FUNCS_IMPLEMENT(set) \
   return hb_##set##_get_unicode_funcs ();
 
-#ifdef HAVE_GLIB
+#if defined(HAVE_UCDN)
+  HB_UNICODE_FUNCS_IMPLEMENT(ucdn)
+#elif defined(HAVE_GLIB)
   HB_UNICODE_FUNCS_IMPLEMENT(glib)
 #elif defined(HAVE_ICU) && defined(HAVE_ICU_BUILTIN)
   HB_UNICODE_FUNCS_IMPLEMENT(icu)
-#elif defined(HAVE_UCDN)
-  HB_UNICODE_FUNCS_IMPLEMENT(ucdn)
 #else
 #define HB_UNICODE_FUNCS_NIL 1
   HB_UNICODE_FUNCS_IMPLEMENT(nil)