bring in math.h to provide prototypes

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@.

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

Revert (leaving the complex math part alone). Some stuff is depending
on this historical behavior; so we're stuck in this stupid situation.
No cookie for me.

Move fabs(3), frexp(3), and modf(3) to libm--nothing has been using
them in libc for a very long time. OK guenther@.

use sys/cdefs.h; pointed out by theo

alias fabsl to fabs on these archs

clear sign bit, instead of comparing to zero and setting x=-x.
fixes special cases, such as neg. zero, and makes C99 conformant
ok miod@, millert@
since there's nothing else in arm's fabs.c, replace 4-clause license
w/ the one at /usr/share/misc/license.template

ARGH, forgot tags.

arm libc support. From NetBSD. currently supports softfloat.