[klibc] SYSCALLS.def: add openat() on 64-bit platforms

We had __openat() as a system call on 32 bits, wrappered in openat.c;
however, the unwrappered system call used on 64-bit platforms was
missing from SYSCALLS.def.

Reported-by: Maximilan Attems <max@stro.at>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/usr/klibc/SYSCALLS.def b/usr/klibc/SYSCALLS.def
index 70838b8..35bcdcf 100644
--- a/usr/klibc/SYSCALLS.def
+++ b/usr/klibc/SYSCALLS.def
@@ -157,6 +157,7 @@
 <!i386,m68k,64> int open::__open(const char *, int, mode_t);
 <?!i386,m68k,64> int openat::__openat(int, const char *, int, mode_t);
 <64> int open(const char *, int, mode_t);
+<64> int openat(int, const char *, int, mode_t);
 ssize_t read(int, void *, size_t);
 ssize_t write(int, const void *, size_t);
 int close(int);