Bug#33812: mysql client incorrectly parsing DELIMITER

Fix parsing of mysql client commands, especially in relation to
single-line comments when --comments was specified.

This is a little tricky, because we need to allow single-line
comments in the middle of statements, but we don't want to allow
client commands in the middle of statements. So in
comment-preservation mode, we go ahead and send single-line
comments to the server immediately when we encounter them on their
own. 

This is still slightly flawed, in that it does not handle a
single-line comment with leading spaces, followed by a client-side
command when --comment has been enabled. But this isn't a new
problem, and it is quite an edge condition. Fixing it would require
a more extensive overall of how the mysql client parses commands.

mysql-test/r/mysql.result

@@ -180,4 +180,10 @@ ERROR at line 1: DELIMITER cannot contain a backslash character
 1
 This is a file starting with UTF8 BOM 0xEFBBBF
 This is a file starting with UTF8 BOM 0xEFBBBF
+delimiter
+1
+2
+2
+2
+2
 End of 5.0 tests

mysql-test/t/mysql.test

@@ -290,4 +290,23 @@ EOF
 --exec $MYSQL < $MYSQLTEST_VARDIR/tmp/bug29323.sql 2>&1
 remove_file $MYSQLTEST_VARDIR/tmp/bug29323.sql;
 
+#
+# Bug #33812: mysql client incorrectly parsing DELIMITER
+#
+# The space and ; after delimiter are important
+--exec $MYSQL -e "select 1 delimiter ;"
+
+#
+# Bug #38158: mysql client regression, can't read dump files
+#
+--write_file $MYSQLTEST_VARDIR/tmp/bug38158.sql
+-- Testing
+--
+delimiter ||
+select 2 ||
+EOF
+--exec $MYSQL < $MYSQLTEST_VARDIR/tmp/bug38158.sql 2>&1
+--exec $MYSQL -c < $MYSQLTEST_VARDIR/tmp/bug38158.sql 2>&1
+remove_file $MYSQLTEST_VARDIR/tmp/bug38158.sql;
+
 --echo End of 5.0 tests