Limit flammenwehrfer's output length for github issues

Otherwise github sadly rejects the edit
11 jobs for !49 with fix/flammenwehrfer-output-length in 20 minutes and 23 seconds (queued for 6 seconds)
latest merge request
Name Stage Failure
failed
gruppen: [4, iComputerfreak/DerCompiler, 1] Run
[0020]    }
[0021]

----------------------------------------
Ran 40 tests, of which 40 failed.
A full report for each test can be found at ../../../mjtest/reports/12-12-21_12-26-53_compile-firm.failed
Ran 411 tests, of which 105 failed.
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

failed
gruppen: [3, larsk21/compiler-minijava, 1] Run
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1