lib/msun: Cleanup after $FreeBSD$ removal

Remove no longer needed explicit inclusion of sys/cdefs.h.

PR: 276669
MFC after: 1 week

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Implementations of cexpl()

The change implements cexpl() for both ld80 and ld128 architectures.
Testing was done on x86_64 and aarch64 systems.

Along the way sincos[fl]() use an optimization that reduces the argument
to being done one rather than twice. This optimization actually pointed
to a bug in the ld128 version of sincosl(), which is now fixed. In
addition, the minmax polynomial coefficients for sincosl() have been
updated.

A concise log of the file-by-file changes follows.

* include/complex.h:
. Add a prototype for cexpl().

* lib/msun/Makefile:
. Add s_cexpl.c to the build.
. Setup a link for cexpl.3 to cexp.3.

* lib/msun/Symbol.map:
. Expose cexpl symbol in libm shared library.

* lib/msun/ld128/s_cexpl.c:
* Implementation of cexpl() for 128-bit long double architectures.
Tested on an aarch64 system.

* lib/msun/ld80/s_cexpl.c:
* Implementation of cexpl() for Intel 80-bit long double.

* lib/msun/man/cexp.3:
. Document cexpl().

* lib/msun/man/complex.3:
. Add a BUGS section about cpow[fl].

* lib/msun/src/s_cexp.c:
. Include float.h for weak references on 53-bit long double targets.
. Use sincos() to reduce argument reduction cost.

* lib/msun/src/s_cexpf.c:
. Use sincosf() to reduce argument reduction cost.

* lib/msun/src/k_sincosl.h:
. Catch up with the new minmax polynomial coefficients for the kernel for
the 128-bit cosl() implementation.
. BUG FIX: *cs was used where *sn should have been. This means that sinl()
was no computed correctly when iy != 0.

* lib/msun/src/s_cosl.c:
. Include fpmath.h to get access to IEEEl2bits.
. Replace M_PI_4 with pio4, a 64-bit or 113-bit approximation for pi / 4.

PR: 216862
MFC after: 1 week

Get the fix in back by reverting the part accidentally included in r354491.

This brings back r354467.

MFC after: 1 week
Sponsored by: The FreeBSD Foundation

libcompat: build 32-bit rtld and ldd as part of "everything"

Alter bsd.compat.mk to set MACHINE and MACHINE_ARCH when included
directly so MD paths in Makefiles work. In the process centralize
setting them in LIBCOMPATWMAKEENV.

Alter .PATH and CFLAGS settings in work when the Makefile is included.

While here only support LIB32 on supported platforms rather than always
enabling it and requiring users of MK_LIB32 to filter based
TARGET/MACHINE_ARCH.

The net effect of this change is to make Makefile.libcompat only build
compatability libraries.

Changes relative to r354449:

Correct detection of the compiler type when bsd.compat.mk is used
outside Makefile.libcompat. Previously it always matched the clang
case.

Set LDFLAGS including the linker emulation for mips where -m32 seems to
be insufficent.

Reviewed by: imp, kib (origional version in r354449)
Obtained from: CheriBSD (conceptually)
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D22251

Fix declaration of S1 by swapping misplaced ',' and ';'.

Reported by: kargl
Obtained from: OpenBSD (tb@openbsd.org)
MFC after: 1 week

Revert change accidentally included in r354465.

Will recommit with a proper commit message shortly.

Revert r354449: libcompat: build 32-bit rtld and ldd as part of "everything"

Additional testing is required..

Implement sincos, sincosf, and sincosl.
The primary benefit of these functions is that argument
reduction is done once instead of twice in independent
calls to sin() and cos().

* lib/msun/Makefile:
. Add s_sincos[fl].c to the build.
. Add sincos.3 documentation.
. Add appropriate MLINKS.

* lib/msun/Symbol.map:
. Expose sincos[fl] symbols in dynamic libm.so.

* lib/msun/man/sincos.3:
. Documentation for sincos[fl].

* lib/msun/src/k_sincos.h:
. Kernel for sincos() function. This merges the individual kernels
for sin() and cos(). The merger offered an opportunity to re-arrange
the individual kernels for better performance.

* lib/msun/src/k_sincosf.h:
. Kernel for sincosf() function. This merges the individual kernels
for sinf() and cosf(). The merger offered an opportunity to re-arrange
the individual kernels for better performance.

* lib/msun/src/k_sincosl.h:
. Kernel for sincosl() function. This merges the individual kernels
for sinl() and cosl(). The merger offered an opportunity to re-arrange
the individual kernels for better performance.

* lib/msun/src/math.h:
. Add prototytpes for sincos[fl]().

* lib/msun/src/math_private.h:
. Add RETURNV macros. This is needed to reset fpsetprec on I386
hardware for a function with type void.

* lib/msun/src/s_sincos.c:
. Implementation of sincos() where sin() and cos() were merged into
one routine and possibly re-arranged for better performance.

* lib/msun/src/s_sincosf.c:
. Implementation of sincosf() where sinf() and cosf() were merged into
one routine and possibly re-arranged for better performance.

* lib/msun/src/s_sincosl.c:
. Implementation of sincosl() where sinl() and cosl() were merged into
one routine and possibly re-arranged for better performance.

PR: 215977, 218300
Submitted by: Steven G. Kargl <sgk@troutmask.apl.washington.edu>
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D10765