Merge changes Ia7dd2ded,I9e85a9ae,Id7436404 into main

* changes:
  Fix uchar.mbrtoc16_zero_len for glibc and musl.
  Fix mbrtoc32 tests for out of range code points.
  Fix mbrtoc32 test for musl and glibc.
diff --git a/libc/private/thread_private.h b/libc/private/thread_private.h
index 1f9eeb6..1a13690 100644
--- a/libc/private/thread_private.h
+++ b/libc/private/thread_private.h
@@ -29,7 +29,6 @@
 
 #define _ARC4_LOCK() _thread_arc4_lock()
 #define _ARC4_UNLOCK() _thread_arc4_unlock()
-#define _ARC4_ATFORK(f) pthread_atfork(NULL, NULL, (f))
 
 extern volatile sig_atomic_t _rs_forked;
 
diff --git a/libc/upstream-netbsd/android/include/rand48.h b/libc/upstream-netbsd/lib/libc/stdlib/rand48.h
similarity index 80%
rename from libc/upstream-netbsd/android/include/rand48.h
rename to libc/upstream-netbsd/lib/libc/stdlib/rand48.h
index 1279906..1ad8b0d 100644
--- a/libc/upstream-netbsd/android/include/rand48.h
+++ b/libc/upstream-netbsd/lib/libc/stdlib/rand48.h
@@ -18,10 +18,10 @@
 
 #include <stdlib.h>
 
-__LIBC_HIDDEN__ void		__dorand48(unsigned short[3]);
-__LIBC_HIDDEN__ unsigned short	__rand48_seed[3];
-__LIBC_HIDDEN__ unsigned short	__rand48_mult[3];
-__LIBC_HIDDEN__ unsigned short	__rand48_add;
+extern void		__dorand48(unsigned short[3]);
+extern unsigned short	__rand48_seed[3];
+extern unsigned short	__rand48_mult[3];
+extern unsigned short	__rand48_add;
 
 #define	RAND48_SEED_0	(0x330e)
 #define	RAND48_SEED_1	(0xabcd)