MDEV-10139 Support for SEQUENCE objects

Working features:
CREATE OR REPLACE [TEMPORARY] SEQUENCE [IF NOT EXISTS] name
    [ INCREMENT [ BY | = ] increment ]
    [ MINVALUE [=] minvalue | NO MINVALUE ]
    [ MAXVALUE [=] maxvalue | NO MAXVALUE ]
    [ START [ WITH | = ] start ] [ CACHE [=] cache ] [ [ NO ] CYCLE ]
    ENGINE=xxx COMMENT=".."
SELECT NEXT VALUE FOR sequence_name;
SELECT NEXTVAL(sequence_name);
SELECT PREVIOUS VALUE FOR sequence_name;
SELECT LASTVAL(sequence_name);

SHOW CREATE SEQUENCE sequence_name;
SHOW CREATE TABLE sequence_name;
CREATE TABLE sequence-structure ... SEQUENCE=1
ALTER TABLE sequence RENAME TO sequence2;
RENAME TABLE sequence TO sequence2;
DROP [TEMPORARY] SEQUENCE  [IF EXISTS] sequence_names

Missing features
- SETVAL(value,sequence_name), to be used with replication.
- Check replication, including checking that sequence tables are marked
  not transactional.
- Check that a commit happens for NEXT VALUE that changes table data (may
  already work)
- ALTER SEQUENCE. ANSI SQL version of setval.
- Share identical sequence entries to not add things twice to table list.
- testing insert/delete/update/truncate/load data
- Run and fix Alibaba sequence tests (part of mysql-test/suite/sql_sequence)
- Write documentation for NEXT VALUE / PREVIOUS_VALUE
- NEXTVAL in DEFAULT
  - Ensure that NEXTVAL in DEFAULT uses database from base table
- Two NEXTVAL for same row should give same answer.
- Oracle syntax sequence_table.nextval, without any FOR or FROM.
- Sequence tables are treated as 'not read constant tables' by SELECT; Would
  be better if we would have a separate list for sequence tables so that
  select doesn't know about them, except if refereed to with FROM.

Other things done:
- Improved output for safemalloc backtrack
- frm_type_enum changed to Table_type
- Removed lex->is_view and replaced with lex->table_type. This allows
  use to more easy check if item is view, sequence or table.
- Added table flag HA_CAN_TABLES_WITHOUT_ROLLBACK, needed for handlers
  that want's to support sequences
- Added handler calls:
 - engine_name(), to simplify getting engine name for partition and sequences
 - update_first_row(), to be able to do efficient sequence implementations.
 - Made binlog_log_row() global to be able to call it from ha_sequence.cc
- Added handler variable: row_already_logged, to be able to flag that the
  changed row is already logging to replication log.
- Added CF_DB_CHANGE and CF_SCHEMA_CHANGE flags to simplify
  deny_updates_if_read_only_option()
- Added sp_add_cfetch() to avoid new conflicts in sql_yacc.yy
- Moved code for add_table_options() out from sql_show.cc::show_create_table()
- Added String::append_longlong() and used it in sql_show.cc to simplify code.
- Added extra option to dd_frm_type() and ha_table_exists to indicate if
  the table is a sequence. Needed by DROP SQUENCE to not drop a table.

sql/udf_example.c

@@ -56,7 +56,7 @@
 **
 ** Function 'myfunc_int' returns summary length of all its arguments.
 **
-** Function 'sequence' returns an sequence starting from a certain number.
+** Function 'udf_sequence' returns an sequence starting from a certain number.
 **
 ** Function 'myfunc_argument_name' returns name of argument.
 **
@@ -80,7 +80,7 @@
 ** CREATE FUNCTION metaphon RETURNS STRING SONAME "udf_example.so";
 ** CREATE FUNCTION myfunc_double RETURNS REAL SONAME "udf_example.so";
 ** CREATE FUNCTION myfunc_int RETURNS INTEGER SONAME "udf_example.so";
-** CREATE FUNCTION sequence RETURNS INTEGER SONAME "udf_example.so";
+** CREATE FUNCTION udf_sequence RETURNS INTEGER SONAME "udf_example.so";
 ** CREATE FUNCTION lookup RETURNS STRING SONAME "udf_example.so";
 ** CREATE FUNCTION reverse_lookup RETURNS STRING SONAME "udf_example.so";
 ** CREATE AGGREGATE FUNCTION avgcost RETURNS REAL SONAME "udf_example.so";
@@ -162,9 +162,9 @@ double myfunc_double(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
 my_bool myfunc_int_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
 longlong myfunc_int(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
 		    char *error);
-my_bool sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
- void sequence_deinit(UDF_INIT *initid);
-longlong sequence(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
+my_bool udf_sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
+ void udf_sequence_deinit(UDF_INIT *initid);
+longlong udf_sequence(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
 		   char *error);
 my_bool avgcost_init( UDF_INIT* initid, UDF_ARGS* args, char* message );
 void avgcost_deinit( UDF_INIT* initid );
@@ -642,7 +642,7 @@ my_bool myfunc_int_init(UDF_INIT *initid __attribute__((unused)),
   or 1 if no arguments have been given
 */
 
-my_bool sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
+my_bool udf_sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
 {
   if (args->arg_count > 1)
   {
@@ -659,22 +659,22 @@ my_bool sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
   }
   bzero(initid->ptr,sizeof(longlong));
   /* 
-    sequence() is a non-deterministic function : it has different value 
+    udf_sequence() is a non-deterministic function : it has different value 
     even if called with the same arguments.
   */
   initid->const_item=0;
   return 0;
 }
 
-void sequence_deinit(UDF_INIT *initid)
+void udf_sequence_deinit(UDF_INIT *initid)
 {
   if (initid->ptr)
     free(initid->ptr);
 }
 
-longlong sequence(UDF_INIT *initid __attribute__((unused)), UDF_ARGS *args,
-                  char *is_null __attribute__((unused)),
-                  char *error __attribute__((unused)))
+longlong udf_sequence(UDF_INIT *initid __attribute__((unused)), UDF_ARGS *args,
+                      char *is_null __attribute__((unused)),
+                      char *error __attribute__((unused)))
 {
   ulonglong val=0;
   if (args->arg_count)