Clear buffer values on fifo buffer recreation

The cached WordDB/Highlighters/FifoReader are not relevant and are
better fully rebuilt than updated. This speeds up rebuilding the
WordDB of big fifo buffers such as a `git log`.

src/buffer_utils.cc

@@ -178,6 +178,7 @@ Buffer* create_fifo_buffer(String name, int fd, Buffer::Flags flags, bool scroll
     if (buffer)
     {
         buffer->flags() |= Buffer::Flags::NoUndo | flags;
+        buffer->values().clear();
         buffer->reload({StringData::create({"\n"})}, ByteOrderMark::None, EolFormat::Lf, {InvalidTime, {}, {}});
     }
     else