Make fixes and improvements

- Fix handling of precision in hex float formatting
- Enhance the cocmd interpreter for system() and popen()
- Manually ran the Lua unit tests, which are now passing
- Let stdio i/o operations happen when file is in error state
- We're now saving and restoring xmm in ftrace out of paranoia

libc/stdio/fread_unlocked.c

@@ -43,7 +43,7 @@ size_t fread_unlocked(void *buf, size_t stride, size_t count, FILE *f) {
   ssize_t rc;
   size_t n, m;
   struct iovec iov[2];
-  if (f->state) {
+  if (!stride) {
     return 0;
   }
   if ((f->iomode & O_ACCMODE) == O_WRONLY) {