[SM-PLUGINS] compatibility plugin issue

[THEON C. C. <com...@gm...>]

I'm getting the following error trying to install the latest compatibility
plugin on squirrelmail version 1.4.5:

patch -p0 < compatibility/patches/compatibility_patch-1.4.5.diff
patching file ../include/validate.php
Hunk #1 FAILED at 43.
1 out of 1 hunk FAILED -- saving rejects to file ../include/validate.php.rej

I really need to install the change_sql_pass plugin and without the
compatibility plugin it won't work. Your help is greatly appreciated.