bsd.lib.mk: Exclude MD linker-generated crud from expected symbols.

Not entirely sure why these symbols like _init/_fini/_end on x86 or
__bss_start__/__bss_end__ on aarch64 or _GLOBAL_OFFSET_TABLE_ on hppa
are exported at all, but it's something the linker is doing
automatically -- and unnecessarily, since libraries with explicit
version scripts don't export these -- and I'm not sure there's any way
to suppress it.

This way, most *.expsym lists can be machine-independent, which will
help keep maintenance burden much lower.

Currently we have only one *.expsym file for a library that _doesn't_
use a version script, libm -- fix that up to reduce the crud. (That
one already happens to have a lot of machine-dependent exports
because of differences in floating-point ABIs so the linker-generated
MD symbol crud wasn't much more of a maintenance burden in this case,
but this maintenance burden is why I haven't aggressively gone around
creating *.expsym files for other libraries.)

branches: 1.7.2;
libm: Factor out common expected symbol list.

Should substantially reduce the maintenance burden.

libm: Define lgamma_r, lgammal, lgammal_r on non-IEEE754.

Missing internal aliases _lgamma_r and _lgammal_r -- TBD.

PR 57881

libm: Do the weak alias dance for asin, acos, atan.

These are used internally by the complex trig functions, so they need
weak aliases.

libm: Add frexpf and frexpl on VAX.

These are trivial subroutines, not symbol aliases, for separate
reasons:

- frexpf has a different ABI from frexp (float vs double argument)

- frexp is defined in libc, not libm, so although long double is the
same as double, frexpl can't be an alias in libm of a symbol
defined in libc

libm: Add rintl, rintf to non-IEEE754 architectures.

While here, delete #ifdef to handle ns32k -- I don't think that's
gonna be relevant any time soon; in case you hadn't noticed, the
world has moved on from ns32k to vax by now.

PR 57881

libm/arch/vax: Do the weak alias dance for finite, finitef.

These are used internally.

libm: Memorialize expected symbols on various architectures.

This will reduce the risk of accidentally adding or deleting the
wrong symbols while fixing the aliases.

(This is all the architectures I have a build tree for handy; can add
other architectures like m68k later.)