Changes on 18 August to functions.php were intended to correct issue with the $icon_t...

Changes on 18 August to functions.php were intended to correct issue with the $icon_theme preference not being grabbed correctly.  Unfortunately, it has come to light that this change has broken several other preferences.  This patch undoes the changes from 18 August and changes the handling of the $icon_theme pref so that it is handled correctly.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@11623 7612ce4b-ef26-0410-bec9-ea0150e637f0