The random number seed generator was creating float values that, when fed to mt_srand...

The random number seed generator was creating float values that, when fed to mt_srand(), which expects an integer, were seen as zero on some systems because it was such a large number.  This fix takes a sub-string of the seed's MD5 before converting it to an integer in order to fix that problem.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@13322 7612ce4b-ef26-0410-bec9-ea0150e637f0