ci: Update Travis CI configuration Remove python dependency workaround. Use clang 5 (provided by Travis CI). Add GCC-8 and remove GCC-6. Remove unused clang stuff in 64-bit script.
ci: Update Travis CI configuration Remove python dependency workaround. Use clang 5 (provided by Travis CI). Add GCC-8 and remove GCC-6. Remove unused clang stuff in 64-bit script.