Allow override of DUN settings

Allow override of system DUN settings by setting
persist.sys.dun.override
to one of the following values:
2 = not set, 0 = DUN not required, 1 = DUN required
If the prop is not set or is set to an invalid value the system setting
will be used.

Change-Id: I296f303a23351e4ab29898895abfcd313c747db9
Keyguard: Fix PIN layout on sw320dp-mdpi devices

Fix a long standing lockscreen layout problem that was introduced in 4.2

Before: http://i.imgur.com/9sVKHRR.png
After: http://i.imgur.com/DLY4DRu.png

Change-Id: Ia3cdc0d10217a0a2504a7287f480d9f036e66eee