'SHOW GRANTS' syntax is added 
  'SHOW GRANTS FOR CURRENT_USER' syntax is added
  'SHOW GRANTS FOR CURRENT_USER()' syntax is added
 CURRENT_USER without parens in expressions(SELECT CURRENT_USER;) 


mysql-test/r/grant2.result:
  WL1368: SHOW GRANTS FOR CURRENT USER
mysql-test/r/grant_cache.result:
  WL1368: SHOW GRANTS FOR CURRENT USER
mysql-test/t/grant2.test:
  WL1368: SHOW GRANTS FOR CURRENT USER
mysql-test/t/grant_cache.test:
  WL1368: SHOW GRANTS FOR CURRENT USER
sql/lex.h:
  WL1368: SHOW GRANTS FOR CURRENT USER
sql/sql_yacc.yy:
  WL1368: SHOW GRANTS FOR CURRENT USER