Add new resource configurations for screen width/height in "dp".

You can now specify resource configuration variants "wNNNdp"
and "hNNNdp".  These are the minimum screen width/height in "dp"
units.  This allows you to do things like have your app adjust
its layout based only on the about of horizontal space available.

This introduces a new configuration change flag for screen size.
Note that this configuration change happens each time the orientation
changes.  Applications often say they handle the orientation change
to avoid being restarted at a screen rotation, and this will now
cause them to be restarted.  To address this, we assume the app can
handle this new config change if its target SDK version is < ICS.

Change-Id: I22f8afa136b4f274423978c570fa7c9855040496