added tests for testing structure of mysql db


client/mysqltest.c:
  extend "replace" to column names
  extend "disable_result_log" to output of --exec commad
mysql-test/install_test_db.sh:
  corrected wrong column definitions (as a result of tests)
mysql-test/mysql-test-run.sh:
  export MYSQL and MYSQL_FIX_SYSTEM_TABLES + 
  added option --result-file for *.opt files
scripts/mysql_fix_privilege_tables.sh:
  added new options to using in tests + 
  added new alters (as a result of new tests)
scripts/mysql_fix_privilege_tables.sql:
  added new alters (as a result of new tests)
scripts/mysql_install_db.sh:
  corrected definition of tables_priv.Table_name