WL#2763 - MySQL plugin interface: step 1
Manual merge from CNET tree.


include/ft_global.h:
  Default parser added.
include/my_global.h:
  dlopen related code moved from sql_udf.cc into my_global.h
include/myisam.h:
  Added fulltext parser to MI_KEYDEF
libmysqld/Makefile.am:
  Added LIBDIR macro.
mysql-test/r/connect.result:
  Test result fixed: added plugin table
mysql-test/r/information_schema.result:
  Test result fixed: added plugin table.
mysql-test/r/mysqlcheck.result:
  Test result fixed: added plugin table.
mysql-test/r/system_mysql_db.result:
   Test fixed: added plugin table
mysql-test/t/system_mysql_db_fix.test:
   Test fixed: added plugin table
scripts/mysql_create_system_tables.sh:
  Added mysql.plugin table.
scripts/mysql_fix_privilege_tables.sql:
  Added mysql.plugin table.
sql/Makefile.am:
  Added LIBDIR macro.
sql/ha_myisam.cc:
  Pass fulltext parser from sql to myisam layer.
sql/lex.h:
  Plugin related symbols.
sql/mysqld.cc:
  Initialize/deinitialize plugins, pass opt_plugin_dir.
  plugin-dir renamed to plugin_dir.
  plugin_dir is relative to mysql_home now.
sql/set_var.cc:
  plugin_dir added to SHOW VARIABLES.
sql/share/errmsg.txt:
  Plugin related error messages.
sql/sql_class.h:
  Added parser to Key class.
  Hold parser_name instead of plugin in Key class.
sql/sql_lex.h:
  INSTALL/UNINSTALL PLUGIN commands.
sql/sql_parse.cc:
  INSTALL/UNINSTALL PLUGIN commands.
sql/sql_show.cc:
  SHOW CREATE TABLE: output parser name if index was created WITH PARSER.
sql/sql_table.cc:
  Pass fulltext parser from yacc to sql layer.
sql/sql_udf.cc:
  dlopen related code moved into my_global.h.
  Implemented better check for UDF path.
  UDF loads libraries that are under plugin_dir now.
sql/sql_yacc.yy:
  INSTALL/UNINSTALL PLUGIN syntax.
  Added WITH PARSER syntax to CREATE/ALTER TABLE/INDEX.
  opt_fulltext_parser must allocate memory, since it will be used afterwards.
sql/table.cc:
  Save/restore fulltext parser in extra data segment.
  Added DBUG_PRINTs.
storage/myisam/ft_boolean_search.c:
  Split functions so they can be used by fulltext parser.
  Use fulltext parser if specified.
storage/myisam/ft_nlq_search.c:
  Use fulltext parser.
storage/myisam/ft_parser.c:
  Split functions so they can be used by fulltext parser.
  Use fulltext parser if specified.
storage/myisam/ft_static.c:
  Default fulltext parser added.
storage/myisam/ft_update.c:
  Use fulltext parser.
storage/myisam/ftdefs.h:
  FTB_PARAM moved into plugin.h and renamed to MYSQL_FTPARSER_BOOLEAN_INFO.
storage/myisam/mi_open.c:
  Set default parser.