Correct the location of the tags file to ignore.

Ignore src/bkl/tags, all the sources are there, and not under src itself, and
so is the tags file.
Add a file listing user-visible changes in the latest release.

Describe the changes since 1.2.4.
Allow specifying "outputs" property for the actions.

This is used by the makefile-based toolsets to generate dependencies on the
outputs of the action instead of a special phony target corresponding to the
target itself, which is better as it avoids rebuilding everything depending
on the action during each make run.
Increase version to 1.2.5.

Also fix the date in the change log.