musl does not support legacy 32-bit-off_t whatsoever. off_t is always
64 bit, and correct programs that use off_t and the standard functions
will just work out of the box. (on glibc, they would require
-D_FILE_OFFSET_BITS=64 to work.) however, some programs instead define
_LARGEFILE64_SOURCE and use alternate versions of all the standard
types and functions with "64" appended to their names.

we do not want code to actually get linked against these functions
(it's ugly and inconsistent), so macros are used instead of prototypes
with weak aliases in the library itself. eventually the weak aliases
may be added at the library level for the sake of using code that was
originally built against glibc, but the macros will still be the
desired solution in the headers.

in6_* is in the reserved namespace, so this is valid

these were at best of limited usefulness (for bootstrapping new
systems, mainly) and at worst caused real kernel headers to get
overwritten when upgrading libc.

in case they're needed by anyone, the exact same files are now
available in a new git repository:

git://git.etalabs.net/mini-lkh

this is a nonstandard function so it's not clear what conditions it
should satisfy. my intent is that it be fast and exact for positive
integral exponents when the result fits in the destination type, and
fast and correctly rounded for small negative integral exponents.
otherwise we aim for at most 1ulp error; it seems to differ from pow
by at most 1ulp and it's often 2-5 times faster than pow.

I actually wrote these a month ago but forgot to integrate them. ugly,
probably-harmful-to-use functions, but some legacy apps want them...

- add the rest of the junk traditionally in sys/param.h
- add prototypes for some nonstandard functions
- add _GNU_SOURCE to their source files so the compiler can check proto

fcntl values 1024 and up are universal, arch-independent. later I'll
add some of the other linux-specific ones for notify, leases, pipe
size, etc. here too.

this is legal since sa_* is in the reserved namespace for signal.h,
per posix. note that the sa_restorer field is not used anywhere, so
programs that are trying to use it may still break, but at least
they'll compile. if it turns out such programs actually need to be
able to set their own sa_restorer to function properly, i'll add the
necessary code to sigaction.c later.

I forgot _GNU_SOURCE also has it declared here...

gcc makes this mapping by default anyway, but it will be disabled by
-fno-builtin (and presumably by -std=c99 or similar). for the main
program the error will be reported by the linker, and the issue can
easily be fixed, but for dynamic-loaded so files, the error cannot be
detected until dlopen time, at which point it has become very obscure.

this is necessary so that we can freely add macro versions of some of
the math/complex functions without worrying about breaking tgmath.

DECIMAL_DIG is not the same as LDBL_DIG

type_DIG is the maximimum number of decimal digits that can survive a
round trip from decimal to type and back to decimal.

DECIMAL_DIG is the minimum number of decimal digits required in order
for any floating point type to survive the round trip to decimal and
back, and it is generally larger than LDBL_DIG. since the exact
formula is non-trivial, and defining it larger than necessary may be
legal but wasteful, just define the right value in bits/float.h.

some software apparently uses this and breaks with musl due to
mismatching definitions...

it's not even provided in the library at the moment, but could easily
be provided with weak aliases if desired.

long double and float bessel functions are no longer xsi extensions

presumably broken gcc may generate calls to these, and it's said that
ffmpeg makes use of sincosf.

thanks to the hard work of Szabolcs Nagy (nsz), identifying the best
(from correctness and license standpoint) implementations from freebsd
and openbsd and cleaning them up! musl should now fully support c99
float and long double math functions, and has near-complete complex
math support. tgmath should also work (fully on gcc-compatible
compilers, and mostly on any c99 compiler).

based largely on commit 0376d44a890fea261506f1fc63833e7a686dca19 from
nsz's libm git repo, with some additions (dummy versions of a few
missing long double complex functions, etc.) by me.

various cleanups still need to be made, including re-adding (if
they're correct) some asm functions that were dropped.

the previous version not only failed to work in c++, but also failed
to produce constant expressions, making the macros useless as
initializers for objects of static storage duration.

gcc 3.3 and later have builtins for these, which sadly seem to be the
most "portable" solution. the alternative definitions produce
exceptions (for NAN) and compiler warnings (for INFINITY) on newer
versions of gcc.

these are mostly untested and adapted directly from corresponding byte
string functions and similar.