Dump table of warning counts before all warnings.

* The table of warning counts has links to each warning pattern section,
  which has a new anchor.
* Each warning pattern section has a new link to the 'top' of the table
  of warning counts.
* Background color of unknown warnings is changed to more visible light blue.

BUG: 27698849
Change-Id: Ia3d4a8511bd42f44f6a47afcb9c3889f6d62b9f2