- Travis: Upgrade clang from 3.8.0 to 3.8.1 (provides smaller package for faster downloading)
- Travis: Makes BUILD_COMPONENTS an option
- Followup after #3130 (Boost_LIBRARIES variable no longer exists)
- Builds up ENGINE_LIBRARY_LISTING correctly to pass to pkg-config
- Previous behavior had major flaw and would result in paths in libosrm.pc like: "-L-L"
when the data was "-L/path -lfoo" or just "-lpthread" with no -L/path. It only worked correctly for static libraries
- Refactors to call find_package for boost in one place (helps prepare for upcoming mason PR)