Fix pread/pwrite for LP64.

Unlike on 32-bit systems where off_t is 32-bit, we don't want to
throw away the top 32 bits of an LP64 system's 64-bit off_t.

Change-Id: Ib2e0daeb4fc0b8ab3d1b983d0b371d8f81033b50
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index f31073f..ce79e9c 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -88,8 +88,10 @@
 # file descriptors
 ssize_t     read(int, void*, size_t)        all
 ssize_t     write(int, const void*, size_t)       all
-ssize_t     pread64(int, void*, size_t, off64_t) all
-ssize_t     pwrite64(int, void*, size_t, off64_t) all
+ssize_t     pread64(int, void*, size_t, off64_t) arm,mips,x86
+ssize_t     pread64|pread(int, void*, size_t, off_t) aarch64,x86_64
+ssize_t     pwrite64(int, void*, size_t, off64_t) arm,mips,x86
+ssize_t     pwrite64|pwrite(int, void*, size_t, off_t) aarch64,x86_64
 int         close(int)                      all
 pid_t       getpid()    all
 void*       mmap(void*, size_t, int, int, int, long)  aarch64,x86_64