Change the way some maps are printed.

Before, an anonymous map wound up printing the pc as relative.
Unfortunately, this meant that it was impossible to tell the actual
pc. The new code prints the map name as <anonymous:map_start> and
still prints the pc as relative.

In addition, add the start of the map for map names that begin with a
'[' character.

Bug: 25844836
Change-Id: Ie0b6149dde258fe13f0e5a3e5739d85374512f4b