Remove __builtin_saveregs: gcc hasn't used it for years.

suggested by miod@
ok kettenis@

RELRO means the __{got,plt}_{start,end} symbols are superfluous

ok kettenis@

Hide __fpu_* and make internal _Qp_* calls go direct.

ok kettenis@

Wrap <stdlib.h> so that calls go direct and the symbols not in the
C standard are all weak.
Apply __{BEGIN,END}_HIDDEN_DECLS to gdtoa{,imp}.h, hiding the
arch-specific __strtorx, __ULtox_D2A, __strto

Wrap <stdlib.h> so that calls go direct and the symbols not in the
C standard are all weak.
Apply __{BEGIN,END}_HIDDEN_DECLS to gdtoa{,imp}.h, hiding the
arch-specific __strtorx, __ULtox_D2A, __strtorQ, __ULtoQ_D2A symbols.

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Hide many (194!) symbols that nothing should be using.
Delete exect(2); it wasn't portable across archs and nothing used it.

ports test build by naddy@
ok deraadt@ kettenis@

Explicitly list the symbols permitted to be exported by libc.
This is primed with the current list of exported symbols so it doesn't
change the ABI yet, but will prevent unintentional additions in th

Explicitly list the symbols permitted to be exported by libc.
This is primed with the current list of exported symbols so it doesn't
change the ABI yet, but will prevent unintentional additions in the future
and sets the stage for reductions.

ok deraadt@ kettenis@

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