If we have PHP 4.3.0, we can make SquirrelSpell work with safe_mode.

If we have PHP 4.3.0, we can make SquirrelSpell work with safe_mode.
This also removes the need for the 'cat' program when using older PHP,
easing the use of this plugin under Windows. The patch is provided by
Ray Ferguson, #752314. As I have only PHP 4.1.2, this is not thoroughly
tested code; please test it all so it will be verified to work in many
different environments.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@7819 7612ce4b-ef26-0410-bec9-ea0150e637f0