Revert "Break on read errors in xs_read()."

This reverts commit a7076780a34530077341c57721301ddc4d975a00.

xs_io.h

@@ -53,8 +53,7 @@ xs_val *xs_read(FILE *f, int *sz)
         if ((n = sizeof(tmp)) > size)
             n = size;
 
-        if ((r = fread(tmp, 1, n, f)) <= 0)
-            break;
+        r = fread(tmp, 1, n, f);
 
         /* open room */
         s = xs_realloc(s, rdsz + r);