Change error and fatal messages to start with lowercase and not
end with a period. Note a few very common messages were left
as-is, just in case some other tools parse them.
Also modify the test known-good-output to satisfy the messages.
This reverts commit 6264deece3.
Further investigation discovers that the real issue is that
GNU Emacs compile mode doesn't have a matching regex for GNU
make error messages generated when targets fail. I submitted
a patch to GNU Emacs adding a matcher for compile mode.
In order to fix SV 12267 we were marking the prerequisites of
implicit (pattern) targets that existed elsewhere in the makefile
as precious to keep them from being deleted as intermediate files.
However this also keeps them from being deleted on error. Instead
mark them as secondary.
* tests/scripts/targets/DELETE_ON_ERROR: Test DELETE_ON_ERROR.
