Make more fixes and improvements

- Remove PAGESIZE constant
- Fix realloc() documentation
- Fix ttyname_r() error reporting
- Make forking more reliable on Windows
- Make execvp() a few microseconds faster
- Make system() a few microseconds faster
- Tighten up the socket-related magic numbers
- Loosen restrictions on mmap() offset alignment
- Improve GetProgramExecutableName() with getenv("_")
- Use mkstemp() as basis for mktemp(), tmpfile(), tmpfd()
- Fix flakes in pthread_cancel_test, unix_test, fork_test
- Fix recently introduced futex stack overflow regression
- Let sockets be passed as stdio to subprocesses on Windows
- Improve security of bind() on Windows w/ SO_EXCLUSIVEADDRUSE

libc/calls/clock_gettime-mono.c

@@ -17,14 +17,14 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/struct/timespec.h"
+#include "libc/cosmo.h"
 #include "libc/nexgen32e/rdtsc.h"
 #include "libc/nexgen32e/x86feature.h"
 #include "libc/sysv/consts/clock.h"
 #include "libc/sysv/errfuns.h"
-#include "libc/thread/thread.h"
 
 static struct {
-  pthread_once_t once;
+  _Atomic(uint32_t) once;
   struct timespec base_wall;
   uint64_t base_tick;
 } g_mono;
@@ -39,7 +39,7 @@ int sys_clock_gettime_mono(struct timespec *time) {
   uint64_t cycles;
   struct timespec res;
   if (X86_HAVE(INVTSC)) {
-    pthread_once(&g_mono.once, sys_clock_gettime_mono_init);
+    cosmo_once(&g_mono.once, sys_clock_gettime_mono_init);
     cycles = rdtsc() - g_mono.base_tick;
     nanos = cycles / 3;
     *time = timespec_add(g_mono.base_wall, timespec_fromnanos(nanos));