to mistakes from day 1, it has always had semantics inconsistent with
SVR4 and its successors.  In particular, given argument M:

- On Solaris and FreeBSD/{alpha,sparc64}, it clobbers the old flags
  and *sets* the new flag word to M.  (NetBSD, too?)
- On FreeBSD/{amd64,i386}, it *clears* the flags that are specified in M
  and leaves the remaining flags unchanged (modulo a small bug on amd64.)
- On FreeBSD/ia64, it is not implemented.

There is no way to fix fpsetsticky() to DTRT for both old FreeBSD apps
and apps ported from other operating systems, so the best approach
seems to be to kill the function and fix any apps that break.  I
couldn't find any ports that use it, and any such ports would already
be broken on FreeBSD/ia64 and Linux anyway.

By the way, the routine has always been undocumented in FreeBSD,
except for an MLINK to a manpage that doesn't describe it.  This
manpage has stated since 5.3-RELEASE that the functions it describes
are deprecated, so that must mean that functions that it is *supposed*
to describe but doesn't are even *more* deprecated.  ;-)

Note that fpresetsticky() has been retained on FreeBSD/i386.  As far
as I can tell, no other operating systems or ports of FreeBSD
implement it, so there's nothing for it to be inconsistent with.

PR:		75862
Suggested by:	bde

scalbn() implementation from libm.  (The two functions are defined to
be identical, but ldexp() lives in libc for backwards compatibility.)
The old ldexp() implementation...
  - was more complicated than this one
  - set errno instead of raising FP exceptions
  - got some corner cases wrong
    (e.g. ldexp(1.0, 2000) in round-to-zero mode)

The new implementation lives in libc/gen instead of
libc/$MACHINE_ARCH/gen, since we don't need N copies of a
machine-independent file.  The amd64 and i386 platforms
retain their fast and correct MD implementations and
override this one.

operation (by subtracting the absolute result from 0), don't test
for overflow.

This avoids an arithmetic exception when dividing LONG_MIN by 1:
This is the only case that causes overflow, and the resulting value
is correct under 2's compliment arithmetic.

PR:		72024
Approved by:	dwmalone@
Obtained from:	NetBSD
MFC after:	4 days

PR: 70518

for subnormals with one implementation that works.

isnormal() the hard way, rather than relying on fpclassify().  This is
a lose in the sense that we need a total of 12 functions, but it is
necessary for binary compatibility because we have never bumped libm's
major version number.  In particular, isinf(), isnan(), and isnanf()
were BSD libc functions before they were C99 macros, so we can't
reimplement them in terms of fpclassify() without adding a dependency
on libc.so.5.  I have tried to arrange things so that programs that
could be compiled in FreeBSD 4.X will generate the same external
references when compiled in 5.X.  At the same time, the new macros
should remain C99-compliant.

The isinf() and isnan() functions remain in libc for historical
reasons; however, I have moved the functions that implement the macros
isfinite() and isnormal() to libm where they belong.  Moreover,
half a dozen MD versions of isinf() and isnan() have been replaced
with MI versions that work equally well.

Prodded by:	kris