Use rint functions not __rint functions in glibc libm.

Use rint functions not __rint functions in glibc libm.

Continuing the move to use, within libm, public names for libm
functions that can be inlined as built-in functions on many
architectures, this patch moves calls to __rint functions to call the
corresponding rint names instead, with asm redirection to __rint when
the calls are not inlined.  The x86_64 math_private.h is removed as no
longer useful after this patch.

This patch is relative to a tree with my floor patch
<https://sourceware.org/ml/libc-alpha/2018-09/msg00148.html> applied,
and much the same considerations arise regarding possibly replacing an
IFUNC call with a direct inline expansion.

Tested for x86_64, and with build-many-glibcs.py.

	* include/math.h [!_ISOMAC && !(__FINITE_MATH_ONLY__ &&
	__FINITE_MATH_ONLY__ > 0) && !NO_MATH_REDIRECT] (rint): Redirect
	using MATH_REDIRECT.
	* sysdeps/aarch64/fpu/s_rint.c: Define NO_MATH_REDIRECT before
	header inclusion.
	* sysdeps/aarch64/fpu/s_rintf.c: Likewise.
	* sysdeps/alpha/fpu/s_rint.c: Likewise.
	* sysdeps/alpha/fpu/s_rintf.c: Likewise.
	* sysdeps/i386/fpu/s_rintl.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_rint.c: Likewise.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_rint.c: Likewise.
	* sysdeps/ieee754/float128/s_rintf128.c: Likewise.
	* sysdeps/ieee754/flt-32/s_rintf.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_rintl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_rintl.c: Likewise.
	* sysdeps/m68k/coldfire/fpu/s_rint.c: Likewise.
	* sysdeps/m68k/coldfire/fpu/s_rintf.c: Likewise.
	* sysdeps/m68k/m680x0/fpu/s_rint.c: Likewise.
	* sysdeps/m68k/m680x0/fpu/s_rintf.c: Likewise.
	* sysdeps/m68k/m680x0/fpu/s_rintl.c: Likewise.
	* sysdeps/powerpc/fpu/s_rint.c: Likewise.
	* sysdeps/powerpc/fpu/s_rintf.c: Likewise.
	* sysdeps/riscv/rv64/rvd/s_rint.c: Likewise.
	* sysdeps/riscv/rvf/s_rintf.c: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_rint.c: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_rintf.c: Likewise.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_rint.c: Likewise.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_rintf.c: Likewise.
	* sysdeps/x86_64/fpu/multiarch/s_rint.c: Likewise.
	* sysdeps/x86_64/fpu/multiarch/s_rintf.c: Likewise.
	* sysdeps/x86_64/fpu/math_private.h: Remove file.
	* math/e_scalb.c (invalid_fn): Use rint functions instead of
	__rint variants.
	* math/e_scalbf.c (invalid_fn): Likewise.
	* math/e_scalbl.c (invalid_fn): Likewise.
	* sysdeps/ieee754/dbl-64/e_gamma_r.c (__ieee754_gamma_r):
	Likewise.
	* sysdeps/ieee754/flt-32/e_gammaf_r.c (__ieee754_gammaf_r):
	Likewise.
	* sysdeps/ieee754/k_standard.c (__kernel_standard): Likewise.
	* sysdeps/ieee754/k_standardl.c (__kernel_standard_l): Likewise.
	* sysdeps/ieee754/ldbl-128/e_gammal_r.c (__ieee754_gammal_r):
	Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_gammal_r.c (__ieee754_gammal_r):
	Likewise.
	* sysdeps/ieee754/ldbl-96/e_gammal_r.c (__ieee754_gammal_r):
	Likewise.
	* sysdeps/powerpc/powerpc32/fpu/s_llrint.c (__llrint): Likewise.
	* sysdeps/powerpc/powerpc32/fpu/s_llrintf.c (__llrintf): Likewise.