to the compressed page, if there is one.  Previously, the function only
wrote the LSN to the uncompressed page.

It is not clear why recv_recover_page_func() is updating FIL_PAGE_LSN
in the buffer pool.  The log sequence number will be stamped on the
page when it is flushed to disk, in buf_flush_init_for_writing().
I noticed this inconsistency when analyzing Issue #313, but this patch
does not fix it.  That is no surprise, since FIL_PAGE_LSN should only
matter on disk files, not in the buffer pool.