Use correct C++11/C++0x flags depending on the used compiler

See http://gcc.gnu.org/projects/cxx0x.html for details.
Enable clang build in travis
In travis, do out-of-tree build
Also test intallation
In travis, add boost backport from Mapnik to succeed clang build
Merge pull request #117 from OdyX/dev-C++11-fixes

C++11 fixes to get travis build