MFC r355940:

Move all sources from the llvm project into contrib/llvm-project.

This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo". That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.

Updating the vendor area to match this layout is next.

Move all sources from the llvm project into contrib/llvm-project.

This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo". That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.

Updating the vendor area to match this layout is next.

Update compiler-rt to trunk r224034. This brings a number of new
builtins, and also the various sanitizers. Support for these will be
added in a later commit.

Regenerate after r235388.

Add SPARC64 version of div/mod written in assembly.

This version is similar to the code shipped with libgcc. It is based on
the code from the SPARC64 architecture manual, provided without any
restrictions.

Tested by: flo@