iOS: change platform code to support plugins

platform/iphone/os_iphone.h

@@ -45,6 +45,9 @@
 #include "platform/iphone/vulkan_context_iphone.h"
 #endif
 
+extern void godot_ios_plugins_initialize();
+extern void godot_ios_plugins_deinitialize();
+
 class OSIPhone : public OS_Unix {
 private:
 	static HashMap<String, void *> dynamic_symbol_lookup_table;

platform/iphone/os_iphone.mm

@@ -139,9 +139,13 @@ void OSIPhone::deinitialize_modules() {
 	if (ios) {
 		memdelete(ios);
 	}
+
+	godot_ios_plugins_deinitialize();
 }
 
 void OSIPhone::set_main_loop(MainLoop *p_main_loop) {
+	godot_ios_plugins_initialize();
+
 	main_loop = p_main_loop;
 
 	if (main_loop) {