Log Message:
pkgtools/pkglint: update to 5.6.8

Changes since 5.6.7:

In pkgsrc-wip, if the first line of a file contains an expanded CVS Id,
it is not an error but only a note that it should be an unexpanded CVS
Id. The autofix for this no longer inserts a new line but replaces the
existing line.

Several refactorings and small improvements to the existing diagnostics.