WordPress Upgrades: When defining the default filesystem permissions for files/directories, base the value on the existing ABSPATH & index.php file permissions - so as to respect the executable bit (if set) and not set global read if not required.
This sets a minimum permission set to 750 and 640 for directories and files, so any systems requring less permission than that will still need to define the constants themselves. Fixes #20069 

Built from https://develop.svn.wordpress.org/trunk@25469


git-svn-id: http://core.svn.wordpress.org/trunk@25390 1a063a9b-81f0-0310-95a4-ce76da25c4cd