Bug#14589559: ASSERTION `FILE_ENTRY_BUF[2] == 0'

FAILED IN DEACTIVATE_DDL_LOG_ENTRY

deallocate_ddl_log_entry() can be called without having
locked LOCK_gdl. It uses a global buffer for reading and
writing entries in the ddl_log, and since it is not protected
by any mutex, two concurrent threads can overwrite the
content in the global buffer, so it can be different from
what was read.
Thread a reads from entry 1 into global
buffer, thread b reads from entry 2 into global buffer,
thread a writes from global buffer into entry 1
-> entry 1 is not the content of entry 2.

This is especially bad for replace entries, which uses
two phases, and does not deactivate the whole entry
after the first phase, but increases the phase instead.

Fixed by using thread local storage (stack) instead of global
storage (global buffer).

Also added buffer and size arguments to
read/write_ddl_log_file_entry.

Also only read/write first bytes in entries in
deactivate_ddl_log_entry.

Also fixed the scenario where it will try to recover from a server
compiled with a different value of IO_SIZE (very uncommon!)

updated patch with set_ddl_log_entry_from_buf
and removed read_ddl_log_entry.

Manually tested, no test case included.