PR15044 partial fix: Raise real errors instead of returning error texts.

PR15044 partial fix: Raise real errors instead of returning error texts.

* tapset/dyninst/ctime.stp: Instead of returning "cutesy" error texts,
  raise a real error.
* tapset/linux/context-symbols.stp: Ditto.
* tapset/linux/ctime.stp: Ditto.
* testsuite/systemtap.base/ctime.exp: Make test handle "cutesy" error
  tests or real errors.
* testsuite/systemtap.base/ctime.stp: Ditto.
* NEWS: Mention deprecations.