Reduce libm's exports and make internal calls go direct.
All dependencies on libc are now via reserved/standardized names.

ok kettenis@ millert@ deraadt@

Avoid left-shifting a negative integer, which is undefined. Replace
it with the intended value, in a defined way. From FreeBSD (Dimitry Andric).
ok miod@ deraadt@ kettenis@

test LDBL_MANT_DIG == DBL_MANT_DIG instead of hardcoding 53.
-> test becomes meaningful on vax
No actual change, no bump
okay martynas@

Switch libc and libm to use strong aliases rather than weak aliases
where appropriate. Among other things makes the symbols consistent
across all architectures (notably where ldbl mantissa is 53 bits).

While at it, kill unused LINTLIBRARY/PROTOLIB1 cruft which was there
to trick lint into recording the right prototypes for aliased
functions. Most of the work done at the awesome n2k13 hackathon.

Agreed by kettenis@, guenther@, matthew@.

Get rid of the very ugly lint workarounds: LINTLIBRARY, PROTOLIB,
and a few empty files for lint to chew on.

Remove excessive sys/cdefs.h inclusion
ok guenther millert kettenis

Trick lint into recording the right prototypes in the llib-lm.ln
database on platforms without extended-precision floating-point
support.

Seems like a reasonable approach to millert@.

- 80-bit and quad precision trigonometric and other most
important functions: acosl, asinl, atanl, atan2l, cosl,
sinl, tanl, exp2l, frexpl, ilogbl, ldexpl, logbl, scalbnl,
fabsl, hypotl, powl, sqrtl, rintl, copysignl, nanl, fdiml,
fmaxl, fminl. mostly taken from freebsd, needed alot of
changes to adapt. note, these are all c versions; and are
quite slow when architectures have, e.g. sqrt. assembly
versions will be added afterwards
- make them .weak/__weak_alias to the double precision
versions on other archs
- no need to have two finites. finite() and finitef() are
non-standard 3BSD obsolete versions of isfinite. remove
from libm. make them weak_alias in libc to __isfinite and
__isfinitef instead. similarly make 3BSD obsolete versions
of isinf, isinff, isnan, isnanf weak_aliases to C99's
__isinf, __isinff, __isnan, __isnanf
- remove unused infinity.c. the c library has infinities
for each supported platform
- use STRICT_ASSIGN cast hack for _kernel_rem_pio2, so that
the double version has a chance of working on i386 with
extra precision
- avoid storing multiple copies of the pi/2 array, since
it won't vary
- bump major due to removed finite/finitef. although they
will be in libc, which anything is linked to, minor bump
might be enough
ok millert@. tested by sthen@, jsg@, ajacoutot@, kili@, naddy@

- remove isinff, isnanf. this has been moved to libc
- remove never-enabled signbit. libc has is now
- add C99 implementations, from freebsd, for nan(), nanf() (needed
to write _digittoint for it), exp2(), exp2f(), remquo(), remquof(),
needed STRICT_ASSIGN macro for math_private.h
- bump major
man pages will follow
exp2{,f} has been requested by chl@
ok millert@