Harmonize headers between both dg-extract-results scripts
The header of the python version looked like:
Target is ...
Host is ...
The header of the bash version looked like:
Test run by ... on ...
Target is ...
After this change both headers look like:
Test run by ... on ...
Target is ...
Host is ...
The order of the tests is not the same but since dg-cmp-results.sh it
does not matter much.
contrib/ChangeLog:
* dg-extract-results.py: Print the "Test run" line.
* dg-extract-results.sh: Print the "Host" line.