* sysdeps/generic/bp-checks.h: Use unbounded __memchr

	* sysdeps/generic/bp-checks.h: Use unbounded __memchr
	rather than non-existent __ubp_memchr.
	(CHECK_STRINGopt, CHECK_FCNTL, BOUNDED_N, BOUNDED_1): New macros.
	(_CHECK_STRING, _CHECK_N): New macros.
	(CHECK_STRING, CHECK_N, CHECK_Nopt): Rewrite in terms of _CHECK_*.
	(CHECK_IOCTL): Move inside `#if !__ASSEMBLER__'.
	* sysdeps/alpha/memchr.S: Change strong name to "__memchr".
	Add weak alias "memchr".
	* sysdeps/generic/memchr.c: Likewise.
	* sysdeps/i386/memchr.S: Likewise.
	* sysdeps/ia64/memchr.S: Likewise.
	* sysdeps/m68k/memchr.S: Likewise.
	* sysdeps/sparc/sparc32/memchr.S: Likewise.
	* sysdeps/sparc/sparc64/memchr.S: Likewise.
	* sysdeps/vax/memchr.s: Likewise.