The LLVM Memory Sanitizer support work in progress

I've prepared a report of the past month on MSan:

https://blog.netbsd.org/tnf/entry/the_llvm_memory_sanitizer_support

This is work in progress and I will keep working on MSan. I can already
sanitize trivial programs, but not the larger ones. Sanitizing
LLDB/NetBSD with MSan is still distant.