Fixed bug #68731 finfo_buffer doesn't extract the correct mime with some gifs

The fix for bug #67647 applies here, too.

NEWS

@@ -13,6 +13,8 @@
   . Fixed bug #68827 (Double free with disabled ZMM). (Joshua Rogers)
   . Fixed bug #67647 (Bundled libmagic 5.17 does not detect quicktime files
     correctly). (Anatol)
+  . Fixed bug #68731 (finfo_buffer doesn't extract the correct mime with some
+    gifs). (Anatol)
 
 - Opcache:
   . Fixed bug with try blocks being removed when extended_info opcode

ext/fileinfo/tests/bug68731.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Bug #68731 finfo_buffer doesn't extract the correct mime with some gifs
+--SKIPIF--
+<?php
+if (!class_exists('finfo'))
+	die('skip no fileinfo extension');
+--FILE--
+<?php
+	$buffer = file_get_contents(dirname(__FILE__) . '/68731.gif');
+	$finfo = finfo_open(FILEINFO_MIME_TYPE);
+	echo finfo_buffer($finfo, $buffer);
+?>
+--EXPECT--
+image/gif