• Remove unnecessary VERSION_INT and build-time dependency for "bc"
• Fix a segfault when no mainline kernels are installed
• Allow /tmp to be mounted with noexec
• Rename --show-unstable to --include-unstable, add --hide-unstable, and correct the --help
• Support building on valac < 0.40 (xenial)
• Simplify the download process, fixes some long-standing bugs wrt downloading, cache, installing.