Unable to login with Safari

Bug Overview
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Issue 1:
All versions of Safari (Windows, OSX, iPhone) unable to login to ProjectPier with my current configuration of PHP and Apache. Other users have reported being able to login with Safari... so this may be related to the specific versions of Apache and PHP I am using.

Issue 2:
Any browser, cookies not being cleared when the user closes the browser. This could lead to a false sense of security by the user and is probably more important to fix than the Safari issue listed above.

Server Details
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ProjectPier: 0.8.2
Ubuntu: 6.10
Apache: 2.2.3
PHP: 5.2.1

Steps to reproduce
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Issue 1:
Using Safari, browse to login (projectpier/index.php?c=access&a=login)
Logging in with a correct username/password brings you back to the login screen (projectpier/index.php?c=access&a=login&ref_c=dashboard&ref_a=index)

Checking the "Remember me for 14 days" solves the issue.

Appears to be a problem with the cookies not being set in Safari when the expiration date is within the same day. Setting the expiration date to two weeks in the future solves this problem, but this isn't a very secure solution.

Issue 2:
Login to ProjectPier with any browser. Close the browser and reopen and browse back to ProjectPier to be automatically logged back in.

Proposed solution
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To solve both Issue 1 & Issue 2
In Cookie::setValue, change such that if a NULL $expiration is passed in, pass that NULL value on to the setcookie function so the cookie will be removed when the session is over.