Use qmake builtin debug_and_release.
Remove OS-specific entries from .gitignore.

.gitignore should only store items that are generated by the code in the
repository. If your operating systems generates temporary files, put
those in your .gitignore_global.
More backend changes.
Use qmake builtin debug_and_release.
Add .travis.yml, build out of bin
Merge branch 'gitignore' into DF2014
Merge branch 'morewin' into DF2014
Merge branch 'travis' into DF2014