Highlight the clear button in the recents view when clicked

This commit also makes copies of the ic_notify drawables for the recents
panel to avoid any collisions with possible future changes to the
notification bar UI. (The pressed state drawable was already an unused
leftover resource).

Conflicts:
	packages/SystemUI/res/layout-land/status_bar_recent_panel.xml
	packages/SystemUI/res/layout/status_bar_recent_panel.xml
	packages/SystemUI/res/layout/system_bar_recent_panel.xml