Trigger the display of error and output in sourced commands from the result...

Trigger the display of error and output in sourced commands from the result object's status instead of the presence of text in the error stream
This should be more consistent with the notion of command success/failure and avoids spewing warnings that the user might not care about
There will need to be an option to specify the level of verbosity desired (never show anything, only show failures, errors and warning, everything)

llvm-svn: 170167