- Print signal/core dump like shell/make [feature karen]

  Somehow bash and GNU make can detect which signal caused abnormal
  termination and print it as well as whether core was dumped, for example:

  Aborted (core dumped)
  Segmentation fault

  Would be nice to be just as smart plus, in case of a core, also print where
  it is (normally terminated executable's working directory).

- Tests cleanup [quality karen]

  Need to resolve the following issues in testscript used to test build2:

  * add standard file headers
  * assign ids to all tests
  * @@-issues
  * conformance to testscript style guide
  * &&-expression fix for cat & build
  * use test.{redirect,cleanup} where appropriate
  * cross-testing fixes and conversions