If the title of a trail changes, each member of that trail must be
rebuilt, for its prev/up/next box to reflect the new title.
If the title of a member changes, its next and previous items (if any)
must be rebuilt, for their prev/up/next boxes to reflect the new title.
This ensures that when we do the second phase of the test (edit some
files and refresh), the changes get a different mtime and are picked up,
even if the entire test happened between two 1-second "clock ticks".