In order to make merging of main-line ProblemList files easier in
Preview Projects, I'm planning to add preview project anchors to
the main-line ProblemList files:

Here's my proposed preview project anchor:

#############################################################################

# Preview project specific failures go here at the end of the file.
#
# These are NOT failures that occur with the '--enable-preview' option
# specified; those go in the appropriate ProblemList-enable-preview.txt file.
# These are failures that occur WITHOUT the '--enable-preview' option
# specified AND occur because of some issue with preview project code,
# in either implementation or test code.

#############################################################################