Add retguard macros for libc.
ok deraadt

Instead of trying to handle ffs() with the normal rename-mark-hidden-and-alias
dance, mark it protected. This works better for both gcc and clang: gcc
blocks overriding of internal calls, while clan

Instead of trying to handle ffs() with the normal rename-mark-hidden-and-alias
dance, mark it protected. This works better for both gcc and clang: gcc
blocks overriding of internal calls, while clang permits inlining again.

ok otto@

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Split the non-syscall ASM bits from SYS.h into DEFS.h and use that in the
non-syscall .S source

ok millert@ miod@

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

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@

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Sprinkle END() in some straightforward *.S files that have ENTRY(). The
resulting *.o have "FUNC" symbols with size set.

things for amd64; from art@