The problem is that the server could crash when attempting
to access a non-conformant proc system table. One such case
was a crash when invoking stored procedure related statements
on a 5.1 server with a proc system table in the 5.0 format.

The solution is to validate the proc system table format
before attempts to access it are made. If the table is not
in the format that the server expects, a message is written
to the error log and the statement that caused the table to
be accessed fails.

mysql-test/r/sp-destruct.result:
  Add test case result for Bug#41726
mysql-test/t/sp-destruct.test:
  Add test case for Bug#41726
sql/event_db_repository.cc:
  Update code to use new structures.
sql/sp.cc:
  Describe the proc table format and use it to validate when
  opening a instance of the table.
  Add a check to insure that a error message is written to
  the error log only once.
sql/sql_acl.cc:
  Remove unused variable and use new structure.
sql/sql_acl.h:
  Export field definition.
sql/table.cc:
  Accept the field count and definition in a single structure.
sql/table.h:
  Combine the field count and definition in a single structure.
  Transform function into a class in order to support different
  ways of reporting a error.
  Add a pointer cache to TABLE_SHARE.