Updated the __ACTION_RULE__ to not return its action command output as a single string but instead split it into a list of output lines. This allows Jam code using this output to work correctly independently of what newline character combinations are in use. This was causing problems with Boost Build unit tests which can now be updated to pass.
Consequences & checks:
* Final __ACTION_RULE__ rule parameter has changed from output ? to output-lines *.
* Updated corresponding Jam documentation.
* Updated the all related Boost Build code.
* No code on the Boost trunk uses this rule except for Boost Build itself.
[SVN r42629]
Jurko Gospodnetić