Vendor in a purple-sys wrapper

This code comes from https://github.com/Flared/purple-icq/tree/master/src/purple

It is GPL-3 licensed

src/purple/plugin.rs

@@ -0,0 +1,11 @@
+pub struct Plugin(*mut purple_sys::PurplePlugin);
+
+impl Plugin {
+    pub unsafe fn from_raw(ptr: *mut purple_sys::PurplePlugin) -> Self {
+        Plugin(ptr)
+    }
+
+    pub unsafe fn extra<'a, T>(&mut self) -> &'a mut T {
+        &mut *((*self.0).extra as *mut T)
+    }
+}