Reset bit pos only if it was max

This allows custom use by moving the start of bit reading.

bit-buffer.c

@@ -120,7 +120,8 @@ bb_read (struct BIT_BUFFER *buffer, int size)
           if (!(fread (&(buffer->bits), sizeof (byte), 1, buffer->fp)))
           if (!(fread (&(buffer->bits), sizeof (byte), 1, buffer->fp)))
             return NULL;
             return NULL;
           buffer->first_read = 1;
           buffer->first_read = 1;
-          buffer->pos = 0;
+          if (buffer->pos == BYTE_BIT)
+            buffer->pos = 0;
         }
         }
 
 
       shift_pos = BYTE_BIT - buffer->pos - 1;
       shift_pos = BYTE_BIT - buffer->pos - 1;