Added support for multi statement tests. Use mysqltest internal

command delimiter to change the default delimiter (;) to something
else, a string upto 16 characters is allowed. Separate the sub
queries with ';' and end the whole statement with your own delimiter.

mysql-test/r/multi_statement.result

+select 1;
+1
+1
+select 2;
+select 3;
+select 4||||
+2
+2
+3
+3
+4
+4
+select 5;
+select 6;
+select 50, 'abc';'abcd'
+5
+5
+6
+6
+50	abc
+50	abc
+select "abcd'";'abcd'
+abcd'
+abcd'
+select "'abcd";'abcd'
+'abcd
+'abcd
+select 5'abcd'
+5
+5
+select 'finish';
+finish
+finish

mysql-test/t/multi_statement.test

+select 1;
+delimiter ||||;
+select 2;
+select 3;
+select 4||||
+delimiter 'abcd'||||
+select 5;
+select 6;
+select 50, 'abc';'abcd'
+select "abcd'";'abcd'select "'abcd";'abcd'
+select 5'abcd'
+delimiter ;'abcd'
+select 'finish';