LLDB targeting NetBSD-8.0

I'm moving my efforts of porting LLDB from NetBSD-7.0 to NetBSD-8.0.

I decided that 7.0 isn't worth more effort since libstdc++ is already
too old (no <codecvt>) and it misses support for debug registers and
useful ptrace(2) interfaces for a full-process instrumentation.

I'm going to upgrade the LLVM+Clang+LLDB buildbot to NetBSD HEAD (pre 8.0).