elf-core: Parse vendor-specific notes

ELF notes contain a 'name' field, which specifies a vendor who defines
the format of the note.  Examples are 'FreeBSD' or 'GNU', or it may be
empty for generic notes.

Add a case for FreeBSD-specific notes, leaving Linux and GNU notes,
other vendor-specific notes, and generic notes to be handled by the
existing code for now.

Thanks to Samuel Jacob for reviewing and suggesting improvements.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186973 91177308-0d34-0410-b5e6-96231b3b80d8
elf-core: Improve FreeBSD support and move data extraction to parse time

Extracting thread data at parse time simplifies multi-platform support.
This change adds FreeBSD thread names and auxv info.

Thanks to Samuel Jacob for review, testing, and improvements.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186975 91177308-0d34-0410-b5e6-96231b3b80d8
elf-core: Add helper function for parsing FreeBSD NT_PRSTATUS

This avoids the use of the ELFPrStatus class, which returns to being
used only for Linux.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186976 91177308-0d34-0410-b5e6-96231b3b80d8
elf-core: Remove now-unused compile-time FreeBSD support

This change removes the final instances of compile-time #ifdef magic
from the elf core plugin.  Also rename the classes to ELFLinux... as
they're specific to Linux.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186977 91177308-0d34-0410-b5e6-96231b3b80d8