Define _DIRENT_MATCHES_DIRENT64 regardless

This patch defines _DIRENT_MATCHES_DIRENT64 to either 0 or 1 and adjust its
usage from checking its definition to its value.

Checked on a build for major Linux abis.

	* bits/dirent.h (__INO_T_MATCHES_INO64_T): Define regardless whether
	__INO_T_MATCHES_INO64_T is defined.
	* sysdeps/unix/sysv/linux/bits/dirent.h: Likewise.
	* dirent/alphasort.c: Check _DIRENT_MATCHES_DIRENT64 value instead
	of definition.
	* dirent/alphasort64.c: Likewise.
	* dirent/scandir.c: Likewise.
	* dirent/scandir64-tail.c: Likewise.
	* dirent/scandir64.c: Likewise.
	* dirent/scandirat.c: Likewise.
	* dirent/scandirat64.c: Likewise.
	* dirent/versionsort.c: Likewise.
	* dirent/versionsort64.c: Likewise.
	* include/dirent.h: Likewise.