Remove deprication from mariadbd --debug

--debug is supported by allmost all our other binaries and we should keep
it also in the server to keep option names similar.

mysql-test/suite/innodb_gis/r/check_rtree.result

@@ -1,7 +1,5 @@
 create table t1 (i int, g geometry not null, spatial index (g))engine=innodb;
 SET SESSION debug="+d,rtree_test_check_count";
-Warnings:
-Warning	1287	'@@debug' is deprecated and will be removed in a future release. Please use '@@debug_dbug' instead
 insert into t1 values (1, POINT(1,1));
 insert into t1 values (1, POINT(1.5,1.5));
 insert into t1 values (1, POINT(3,3));

mysql-test/suite/innodb_gis/r/rollback.result

@@ -408,8 +408,6 @@ update t1 set a=point(5,5), b=point(5,5), c=5 where i < 3;
 ERROR 23000: Duplicate entry '5' for key 'c'
 rollback;
 set session debug="+d,row_mysql_crash_if_error";
-Warnings:
-Warning	1287	'@@debug' is deprecated and will be removed in a future release. Please use '@@debug_dbug' instead
 update t1 set a=point(5,5), b=point(5,5), c=5 where i < 3;
 ERROR HY000: Lost connection to MySQL server during query
 insert into t1 values(5, point(5,5), point(5,5), 5);

mysql-test/suite/innodb_gis/r/rtree_compress.result

@@ -42,8 +42,6 @@ count(*)
 0
 SET @saved_dbug = @@SESSION.debug_dbug;
 SET DEBUG='+d,page_copy_rec_list_start_compress_fail';
-Warnings:
-Warning	1287	'@@debug' is deprecated and will be removed in a future release. Please use '@@debug_dbug' instead
 delete from t1;
 select count(*) from t1 where MBRWithin(t1.c2, @g1);
 count(*)

mysql-test/suite/innodb_gis/r/rtree_create_inplace.result

@@ -31,7 +31,5 @@ COUNT(*)
 0
 ALTER TABLE t1 DROP INDEX idx, ADD SPATIAL INDEX idx3(c2);
 SET SESSION debug="+d,row_merge_instrument_log_check_flush";
-Warnings:
-Warning	1287	'@@debug' is deprecated and will be removed in a future release. Please use '@@debug_dbug' instead
 ALTER TABLE t1  DROP INDEX idx3, ADD SPATIAL INDEX idx4(c2), ADD SPATIAL INDEX idx5(c3);
 DROP TABLE t1;