MDEV4732 - Server crashes on attempt to create a SPIDER table with a
           wrong version of mysql.spider_tables
MDEV4733 - Server crashes on attempt to change engine on a SPIDER table

Merged missing changes from revision
alexander.nozdrin@oracle.com-20111219114211-49pqi0wfs9p4o9yi

MDEV-4133: Review InnoDB tablespace allocation patch by Toshikuni Fukaya. If innodb_use_posix_fallocate is set we use posix_fallocate call to extent tablespace allocation instead of pwrite.

modified:
  storage/connect/tabxml.h

            failed in TABLE_SHARE* tdc_acquire_share(THD*, const char*,
            const char*, const char*, uint, uint, TABLE**)

Removed false assertions.

When multiple threads acquire the same previously unused share,
only one thread shall remove share from unused list (the one that
has was_unused == true). Other threads will ignore this step and
may continue even if share is not yet removed from unused list.