clang doesn't propagate attributes like "asm labels" and "visibility(hidden)"
to builtins like mem{set,cpy,move} and __stack_smash_handler. So, when
building with clang, instead mark those as protected visibility to get rid
of the PLT relocations. We can't take the address of them then, but that's
ok: it's a build-time error not a run-time error.

ok kettenis@

Stop exporting _memcpy, an implementation detail of bcopy/memcpy/memmove

ok kettenis@ deraadt@

Use internal names for __errno, _memcpy, memset, and {,_}{set,long}jmp
Eliminate pointless use of PIC_SYM()
Split out DEFS.h from SYS.h like some other archs

ok kettenis@ deraadt@

Add framework for resolving (pun intended) libc namespace issues, using
wrapper .h files and asm labels to let internal calls resolve directly and
not be overridable or use the PLT. Then, apply that framework to most of
the functions in stdio.h, string.h, err.h, and wchar.h. Delete the
should-have-been-hidden-all-along _v?(err|warn)[cx]? symbols while here.

tests clean on i386, amd64, sparc64, powerpc, and mips64

naming feedback from kettenis@ and millert@
ok kettenis@

restructure libc/string + libc/arch/*/string coperation regarding
(potentially) MD versions (function dependent, not filename dependent)
split out memcpy/memmove/bcopy and strchr/index/strrchr/rindex
Bring back amd64 .S versions

And the final touch: switch all architectures temporarily to MI
memcpy.c, which contains syslog + abort for overlapping copies. A nice
harsh undefined behaviour. We will clean the entire userland of the
remaining issues in this catagory, then switch to the optimised memcpy
which skips the memmove check.

I tried to cut this change into pieces, but testing each sub-step on
every architecture is too time consuming and mindnumbing.
ok miod

First pass at removing clauses 3 and 4 from NetBSD licenses.

Not sure what's more surprising: how long it took for NetBSD to
catch up to the rest of the BSDs (including UCB), or the amount of
code that NetBSD has claimed for itself without attributing to the
actual authors.

OK deraadt@

ARGH, forgot tags.

arm libc support. From NetBSD. currently supports softfloat.