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/sock/epoll.c

@@ -1324,7 +1324,7 @@ static textwindows dontinline int sys_epoll_create1_nt(uint32_t flags) {
   struct PortState *port_state;
   struct TsTreeNode *tree_node;
   if (wepoll_init() < 0) return -1;
-  if ((fd = __reservefd()) == -1) return -1;
+  if ((fd = __reservefd(-1)) == -1) return -1;
   port_state = port_new(&ephnd);
   if (!port_state) {
     __releasefd(fd);
@@ -1341,6 +1341,7 @@ static textwindows dontinline int sys_epoll_create1_nt(uint32_t flags) {
   g_fds.p[fd].kind = kFdEpoll;
   g_fds.p[fd].handle = ephnd;
   g_fds.p[fd].flags = flags;
+  g_fds.p[fd].mode = 0140666;
   return fd;
 }