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/calls/statfs.c

@@ -66,3 +66,5 @@ int statfs(const char *path, struct statfs *sf) {
   STRACE("statfs(%#s, [%s]) → %d% m", path, DescribeStatfs(rc, sf));
   return rc;
 }
+
+__weak_reference(statfs, statfs64);