JUNIT output: Avoid hitting sprintf string limit
JUNIT output: Avoid hitting sprintf string limit

Since 7b71266a (Added JUNIT support, 2017-03-16) we have support for JUNIT
output. The routines dealing with the system-out/err streams created a RTE
as sprintf only accepts trings up to 1000 bytes.

t-b/igor-unit-testing-framework,t-b/igor-unit-testing-framework