Increase test timeout
Increase test timeout

There are still tests exceeding the 10 second limit,
although they usually take 1 second.
e.g. https://travis-ci.org/civetweb/civetweb/jobs/76692175

GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver