Improve cosmo's conformance to libc-test

This change addresses various open source compatibility issues, so that
we pass 313/411 of the tests in https://github.com/jart/libc-test where
earlier today we were passing about 30/411 of them, due to header toil.
Please note that Glibc only passes 341/411 so 313 today is pretty good!

- Make the conformance of libc/isystem/ headers nearly perfect
- Import more of the remaining math library routines from Musl
- Fix inconsistencies with type signatures of calls like umask
- Write tests for getpriority/setpriority which work great now
- conform to `struct sockaddr *` on remaining socket functions
- Import a bunch of uninteresting stdlib functions e.g. rand48
- Introduce readdir_r, scandir, pthread_kill, sigsetjmp, etc..

Follow the instructions in our `tool/scripts/cosmocc` toolchain to run
these tests yourself. You use `make CC=cosmocc` on the test repository

libc/calls/sched_setaffinity.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/sched-sysv.internal.h"
 #include "libc/calls/struct/cpuset.h"
@@ -32,7 +33,7 @@ static dontinline textwindows int sys_sched_setaffinity_nt(
   int rc;
   int64_t h, closeme = -1;
 
-  if (!pid /* || pid == getpid() */) {
+  if (!pid || pid == getpid()) {
     h = GetCurrentProcess();
   } else if (__isfdkind(pid, kFdProcess)) {
     h = g_fds.p[pid].handle;