Merge branch 'sg/travis-fixes'

Assorted updates for TravisCI integration.

* sg/travis-fixes:
  travis-ci: use 'set -x' in 'ci/*' scripts for extra tracing output
  travis-ci: set GIT_TEST_HTTPD in 'ci/lib-travisci.sh'
  travis-ci: move setting environment variables to 'ci/lib-travisci.sh'
  travis-ci: introduce a $jobname variable for 'ci/*' scripts