Make fixes and improvements

- Introduce __assert_disable global
- Improve strsignal() thread safety
- Make system call tracing thread safe
- Fix SO_RCVTIMEO / SO_SNDTIMEO on Windows
- Refactor DescribeFoo() functions into one place
- Fix fork() on Windows when TLS and MAP_STACK exist
- Round upwards in setsockopt(SO_RCVTIMEO) on Windows
- Disable futexes on OpenBSD which seem extremely broken
- Implement a better kludge for monotonic time on Windows

libc/runtime/munmap.c

@@ -161,7 +161,7 @@ static noasan int Munmap(char *p, size_t n) {
  * @raises EINVAL if `p+(n-1)` isn't 48-bit
  * @raises EINVAL if `p` isn't 65536-byte aligned
  */
-noasan int munmap(void *p, size_t n) {
+int munmap(void *p, size_t n) {
   int rc;
   size_t toto;
   __mmi_lock();