Revert "Auto-close if you swipe away the last notification."

This reverts commit 8cc36e572876f3bb9197f0109db3042466e5f917.

It didn't work as advertised anyway: It only worked if there are no
persistent notifications, and it also closes the notification area if
the notification is closed by the app itself.

Change-Id: I16f0fb6cf41d20c3a3bd4278446edab780c1fc77

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
Fixes for clang:
PackageInfo is a class, not a struct.
String16 is contained in the android namespace. Do not namespace prefix it
within the android namespace.
Explicitly specify which std classes are necessary to prevent ambiguous
type errors. (map, set)

Change-Id: I0d01477a976e770821ebae8847f8d11b132a15d6