merged 5.0-bugteam -> 5.1-bugteam

client/mysqltest.cc

@@ -1496,6 +1496,9 @@ void show_diff(DYNAMIC_STRING* ds,
   /* determine if we have diff on Windows
      needs special processing due to return values
      on that OS
+     This test is only done on Windows since it's only needed there
+     in order to correctly detect non-availibility of 'diff', and
+     the way it's implemented does not work with default 'diff' on Solaris.
   */
 #ifdef __WIN__
   have_diff = diff_check();