Adding event StartShowNoticeItemNotice with corresponding End

Runs just before outputting the "top" part of a NoticeListItem to HTML
so plugins can jump in and do their thing.

EVENTS.txt

@@ -257,6 +257,22 @@ StartShowNoticeItem: just before showing the notice item
 EndShowNoticeItem: just after showing the notice item
 - $item: the NoticeListItem object being shown
 
+StartShowNoticeItemNotice: just before outputting the "top" notice part of a NoticeListItem to HTML
+- $item: The NoticeListItem object being shown
+
+EndShowNoticeItemNotice: just after outputting the "top" notice part of a NoticeListItem to HTML
+- $item: The NoticeListItem object being shown
+
+StartShowNoticeContent: just before outputting the content part of a Notice
+- $stored: The Notice object
+- $out: HTMLOutputter for writing to
+- $scoped: optional Profile object for permission scoping
+
+EndShowNoticeContent: just after outputting the content part of a Notice, plugins must call this manually
+- $stored: The Notice object
+- $out: HTMLOutputter for writing to
+- $scoped: optional Profile object for permission scoping
+
 StartShowNoticeInfo: just before showing notice info
 - $item: The NoticeListItem object being shown
 

lib/noticelistitem.php

@@ -113,10 +113,13 @@ class NoticeListItem extends Widget
 
     function showNotice()
     {
-        $this->showNoticeTitle();
-        $this->showAuthor();
-        $this->showAddressees();
-        $this->showContent();
+        if (Event::handle('StartShowNoticeItemNotice', array($this))) {
+            $this->showNoticeTitle();
+            $this->showAuthor();
+            $this->showAddressees();
+            $this->showContent();
+            Event::handle('EndShowNoticeItemNotice', array($this-));
+        }
     }
 
     function showNoticeTitle()