branches/zip: Identify records in the modification log by heap_no.
branches/zip: Identify records in the modification log by heap_no.

page_zip_compress(), page_zip_decompress(), page_zip_write_rec():
Note that the end marker of the modification log is 1 byte.

page_zip_find_heap_no(): Remove.

page_zip_apply_log(): Remove parameter "page".  Instead of a 2-byte offset
to the record, decode the heap number using a variable-length code.

page_zip_write_rec(): Check the range of heap_no with debug assertions.
Encode the heap number instead of an offset to the start of the record.

flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,slanterns/server,ollie314/server,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,ollie314/server