* Upstream beta channel update: 63.0.3239.18
* debian/rules:
  - replace allow_posix_link_time_opt=false by use_lld=false, is_cfi=false and use_thin_lto=false
  - rename use_vulcanize GN flag to optimize_webui
  - generate the man page as it's not being built with chromium any longer (since commit 64b961499bebc54fe48478f5e37477252c7887fa)
* debian/patches/arm-neon.patch: refreshed
* debian/patches/disable-sse2: refreshed
* debian/patches/fix-gn-bootstrap.patch: removed, no longer needed
* debian/patches/fix_building_widevinecdm_with_chromium.patch: refreshed
* debian/patches/glibc-2-26-changes.patch: renamed to debian/patches/no-xlocale-header.patch and updated
* debian/patches/revert-Xclang-instcombine-lower-dbg-declare.patch: added
* debian/patches/search-credit.patch: refreshed
* debian/patches/set-rpath-on-chromium-executables.patch: updated
* debian/patches/suppress-newer-clang-warning-flags.patch: updated
* debian/patches/touch-v35: refreshed
* debian/patches/use-clang-versioned.patch: refreshed