Make improvements

- Improved async signal safety of read() particularly for longjmp()
- Started adding cancel cleanup handlers for locks / etc on Windows
- Make /dev/tty work better particularly for uses like `foo | less`
- Eagerly read console input into a linked list, so poll can signal
- Fix some libc definitional bugs, which configure scripts detected

libc/runtime/set_tls.c

@@ -20,7 +20,6 @@
 #include "libc/calls/calls.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
-#include "libc/errno.h"
 #include "libc/nexgen32e/msr.internal.h"
 #include "libc/nt/thread.h"
 #include "libc/sysv/consts/arch.h"
@@ -49,9 +48,7 @@ textstartup void __set_tls(struct CosmoTib *tib) {
     sys_set_tls(tib);
   } else if (IsXnu()) {
     // thread_fast_set_cthread_self has a weird ABI
-    int e = errno;
     sys_set_tls((intptr_t)tib - 0x30);
-    errno = e;
   } else {
     uint64_t val = (uint64_t)tib;
     asm volatile("wrmsr"