Add support for read/write of xmm/ymm registers to lldb.

ok kettenis@, robert@

merge lldb-16.0.6

Shuffle how lldb register contexts are built.

Instead of using #if defined(__arch__) to include / exclude the entire contents
of the NativeRegisterContext implementations, use a single NativeRegiste

Shuffle how lldb register contexts are built.

Instead of using #if defined(__arch__) to include / exclude the entire contents
of the NativeRegisterContext implementations, use a single NativeRegisterContextOpenBSD_arch
which includes the right arch specific register context, and provides a dummy implementation
for unsupported architectures.

This allows building lldb on architectures which do not have a register context implementation
so it can be used as a remote client.

ok patrick@

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Cleanup lldb amd64 support.

- Remove watchpoint support since we do not support hardware watchpoints.

- Support floating point regsisters in the ReadAll/WriteAll interface.

- Standardize the sizes

Cleanup lldb amd64 support.

- Remove watchpoint support since we do not support hardware watchpoints.

- Support floating point regsisters in the ReadAll/WriteAll interface.

- Standardize the sizes used in GerGPRSize() and GetFPRSize() to correspond
to the sizes we get from ptrace.

- Fix the r/w of the mmx registers to map onto the st fp registers instead
of xmm registers.

- Normalize some variable names to be architecture neutral.

ok patrick@

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Import LLVM 10.0.0 release including clang, lld and lldb.

ok hackroom
tested by plenty