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.

- Get rid of debugging support in order to get rid of the V8-specific C
compiler frame size used there so this whole thing is V8/V9-agnostic.
- Use 32-bit function alignment as GCC does when using UltraSPARC I or
higher optimizations.
- Don't waste delay slots when possible.

Unfortunately, this still doesn't make libcompiler_rt a viable replacement
for libgcc on sparc64 though as once installed instead, buildworld times
increase by nearly 60% (which isn't related to these assembler functions).

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@