Improve synchronization

- Fix bugs in kDos2Errno definition
- malloc() should now be thread safe
- Fix bug in rollup.com header generator
- Fix open(O_APPEND) on the New Technology
- Fix select() on the New Technology and test it
- Work towards refactoring i/o for thread safety
- Socket reads and writes on NT now poll for signals
- Work towards i/o completion ports on the New Technology
- Make read() and write() intermittently check for signals
- Blinkenlights keyboard i/o so much better on NT w/ poll()
- You can now poll() files and sockets at the same time on NT
- Fix bug in appendr() that manifests with dlmalloc footers off

libc/zipos/get.c

@@ -87,14 +87,11 @@ struct Zipos *__zipos_get(void) {
           STRACE("__zipos_get(%#s)", program_executable_name);
         } else {
           munmap(map, size);
-          kprintf("__zipos_get(%#s) → eocd not found%n",
-                  program_executable_name);
           STRACE("__zipos_get(%#s) → eocd not found", program_executable_name);
         }
       }
       close(fd);
     } else {
-      kprintf("__zipos_get(%#s) → open failed %m%n", program_executable_name);
       STRACE("__zipos_get(%#s) → open failed %m", program_executable_name);
     }
     once = true;