Report the external display size to the input reader.

The input reader needs this information so that it knows how to
interpolate touches on an external touch screen.

Changed Display so that it asks the WindowManager what the real
display size is (as opposed to the raw display size).  This means
it now takes into the forced display size set by
adb shell am display-size.

Replaced all calls to getRealWidth() / getRealHeight() /
getRealMetrics() in the WindowManager and replaced them with direct
usages of the mCurDisplayWidth / mCurDisplayHeight so that the WM
doesn't end up making a reentrant Binder call into itself.

Fixed the table status bar HeightReceiver so that it updates the
height on all configuration changes since it is possible that the
display size changed independently of an external HDMI display
being plugged / unplugged.

Improved the Display class documentation to make the distinctions
betweeen the various sizes clearer.

Change-Id: I3f75de559d3ebffed532ab46c4ae52c5e7f1da2b