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/runtime/sysconf.c

@@ -49,7 +49,7 @@ long sysconf(int name) {
     case _SC_PAGESIZE:
       return FRAMESIZE;
     case _SC_NPROCESSORS_ONLN:
-      n = GetCpuCount();
+      n = _getcpucount();
       return n > 0 ? n : -1;
     default:
       return -1;