Log Message:
pkgtools/pkglint: update to 19.3.19

Changes since 19.3.18:

Small improvements to edge cases in SUBST blocks.

Small improvements to edge cases in variable assignment and alignment
of the continuation backslashes.

The --source option shows the changes from autofix, even when the
--show-autofix option is not given. This is a welcome side-effect of
making the autofix logging simpler and more predictable.