Original patch by Eric Herman
client/mysql.cc:
Added LAST_VALUE
mysql-test/r/last_value.result:
Testing of LAST_VALUE
mysql-test/t/last_value.test:
Testing of LAST_VALUE
sql/item_func.cc:
Added LAST_VALUE()
sql/item_func.h:
Added LAST_VALUE()
sql/lex.h:
Added LAST_VALUE()
sql/sql_yacc.yy:
Added LAST_VALUE()