Changed size display:

Changed size display:
 - Change to megs if over 1024 k
 - if x < 10, show first digit after decimal point
Created new function (in strings.php) in case sizes should be shown elsewhere.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@790 7612ce4b-ef26-0410-bec9-ea0150e637f0