Add info about SplFileObject::seek() incompatibility to migration guide

Cf. <php/php-src#6434>.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@351790 c90b9560-bf6c-de11-be94-00142212c4b1

Author: cmb69

appendices/migration80/incompatible.xml

@@ -1292,6 +1292,12 @@ $array["key"];
      <methodname>SplFileObject::fgetss</methodname> has been removed.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     <methodname>SplFileObject::seek</methodname> now always seeks to the beginning of the line.
+     Previously, positions <literal>=1</literal> sought to the beginning of the next line.
+    </para>
+   </listitem>
    <listitem>
     <para>
      <methodname>SplHeap::compare</methodname> now specifies a method signature. Inheriting classes