Consolidate alphasort{64} and versionsort{64} implementation

This patch consolidates both alphasort{64} and versionsort{64}
implementation on just the default dirent/alphasort{64}c and
dirent/versionsort{64} respectively.  It changes the logic
to follow the conventions used on other code consolidation:

  * the non-LFS variant is only built for _DIRENT_MATCHES_DIRENT64 being 0.

  * the LFS variant is always built and aliased to getdents for ABIs
    that define _DIRENT_MATCHES_DIRENT64 to 1.

Also on Linux the compat symbol for old non-LFS dirent64 definition
requires a platform-specific scandir64.c.  For powerpc32 and sparcv9
it requires to add specific arch-implementation to override the
generic Linux one because neither ABI exports an compat symbol for
non-LFS alphasort64 and versionsort64 variant.  It is most likely a
bug and it is also not one that can be fixed (in that there would be
existing binaries expecting both meanings of that symbol at its single
existing version, with binaries expecting the new meaning probably much
more common than those expecting the original meaning of that symbol at
that version).

Checked on aarch64-linux-gnu, x86_64-linux-gnu, i686-linux-gnu,
sparcv9-linux-gnu, sparc64-linux-gnu, powerpc-linux-gnu, and
powerpc64le-linux-gnu.

	* dirent/alphasort.c (alphasort): Build iff _DIRENT_MATCHES_DIRENT64 is
	defined.
	* dirent/versionsort.c (versionsort): Likewise.
	* dirent/alphasort64.c (alphasort64): Build regardless and alias to
	alphasort if _DIRENT_MATCHES_DIRENT64 is defined.
	* dirent/versionsort64.c (versionsort64): Likewise.
	* sysdeps/unix/sysv/linux/i386/alphasort64.c: Remove file.
	* sysdeps/unix/sysv/linux/arm/alphasort64.c: Likewise.
	* sysdeps/unix/sysv/linux/arm/versionsort64.c: Likewise.
	* sysdeps/unix/sysv/linux/m68k/alphasort64.c: Likewise.
	* sysdeps/unix/sysv/linux/m68k/versionsort64.c: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/alphasort64.c: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/versionsort64.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/versionsort64.c: Likewise.
	* sysdeps/unix/sysv/linux/alphasort64.c: New file.
	* sysdeps/unix/sysv/linux/versionsort64.c: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/alphasort64.c: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/versionsort64.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/alphasort64.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/versionsort64.c: Likewise.