Move all support library projects to use a single compilation unit

Also cleans up build files to include annotations as an explicit import,
set compileSdkVersion consistently to currentSdk, and remove unnecessary
lines. Removes obsolete API directories in VDC / AVDC.

Because NotificationCompatBase was using @removed APIs, updated that class
to use reflection. Also fixes method visibility in VDC / AVDC.

Bug: 29630077
Test: make and gradle builds successful
Change-Id: Ia9208246837347ce3d8df4adbe6b0ce406d3844a
48 files changed