flash: use -dce no so that Haxe standard library functions aren't rem…

…oved

If another library depends on Feathers UI, builds a .swc for Flash, and depends on functions that were removed, they will break

project.xml

@@ -17,6 +17,11 @@
 		<haxeflag name="--macro" value="AddFlashPropertyMeta.find('feathers')"/>
 		<haxeflag name="--macro" value="AddEventMeta.find('feathers')"/>
 		<haxeflag name="--macro" value="AddDefaultPropertyMeta.find('feathers')"/>
+		<!--
+			don't remove dead code because other libraries that depend on
+			Feathers UI and need to build .swc files too might need it
+		 -->
+		<haxeflag name="-dce" value="no"/>
 	</section>
 
 	<section if="find_missing_docs">