[lldb] [ObjectFile/ELF] Fix recognizing NetBSD images

Split the recognition into NetBSD executables & shared libraries
and core(5) files.

Introduce new owner type: "NetBSD-CORE", as core(5) files are not tagged
in the same way as regular NetBSD executables.

Stop using incorrectly ABI_TAG and ABI_SIZE.  Introduce IDENT_TAG,
IDENT_DECSZ, IDENT_NAMESZ and PROCINFO.

The new values detect correctly the NetBSD images.

The patch has been originally written by Kamil Rytarowski.  I've added
tests and applied minor code changes per review.  The work has been
sponsored by the NetBSD Foundation.

Differential Revision: https://reviews.llvm.org/D42870

llvm-svn: 354466