Greatly expand system() shell code features

The cosmopolitan command interpreter now has 13 builtin commands,
variable support, support for ; / && / || syntax, asynchronous support,
and plenty of unit tests with bug fixes.

This change fixes a bug in posix_spawn() with null envp arg. strace
logging now uses atomic writes for scatter functions. Breaking change
renaming GetCpuCount() to _getcpucount(). TurfWar is now updated to use
the new token bucket algorithm. WIN32 affinity masks now inherit across
fork() and execve().

libc/calls/sched_setscheduler.c

@@ -91,6 +91,7 @@
  * @raise EINVAL if `param` is NULL
  * @raise EINVAL if `policy` is invalid
  * @raise EINVAL if `param` has value out of ranges defined by `policy`
+ * @vforksafe
  */
 int sched_setscheduler(int pid, int policy, const struct sched_param *param) {
   int rc, old;