Make JUnit report stdout/stderr in more cases

In !210 (merged) we made a start to improve the junit output to also include stderr/stdout when appropriate.

However, the patch only handles a few cases, it is reasonably straightforward to handle more cases but the refactoring was a bit more involved than I was prepared to do at the time.

To find more places, look in testlib.py and grep for failBecause. There are examples such as bad stderr and bad stdout which would also benefit from reporting the stderr.

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Trac field	Value
Version	8.6.3
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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