Remove the dependency on unzip. Instead, generate the InnoDB files
with perl.
log_block_checksum_is_ok(): Correct the error message.
recv_scan_log_recs(): Remove the duplicated error message for
log block checksum mismatch.
innobase_start_or_create_for_mysql(): If the server is in read-only
mode or if innodb_force_recovery>=3, do not try to modify the system
tablespace. (If the doublewrite buffer or the non-core system tables
do not exist, do not try to create them.)
innodb_shutdown(): Relax a debug assertion. If the system tablespace
did not contain a doublewrite buffer and if we started up in
innodb_read_only mode or with innodb_force_recovery>=3, it will not
be created.
dict_create_or_check_sys_tablespace(): Set the flag
srv_sys_tablespaces_open when the tables exist.