fix: incorrect parsing of 'Send notifications to this custom email address'

Issue Summary

A list of emails entered into the user_register_notify_mailto field should be separated by a comma, and zero or more spaces.

But when I enter emails like that, they just dont get delivered.

FIX: So in the .module, replace the two lines like:
$emails = preg_split('/,[\w]+/', variable_get('user_register_notify_mailto', $from));
with:
$emails = preg_split('/,[\s]*/', variable_get('user_register_notify_mailto', $from));