flst_read_addr(): Remove assertions. Instead, we will check these
conditions in the callers and avoid a crash in case of corruption.
We will check the conditions more carefully, because the callers
know more exact bounds for the page numbers and the byte offsets
withing pages.

flst_remove(), flst_add_first(), flst_add_last(): Add a parameter
for passing fil_space_t::free_limit. None of the lists may point to
pages that are beyond the current initialized length of the
tablespace.

trx_rseg_mem_restore(): Access the first page of the tablespace,
so that we will correctly recover rseg->space->free_limit
in case some log based recovery is pending.

ibuf_remove_free_page(): Only look up the root page once, and
validate the last page number.

Reviewed by: Debarun Banerjee