check sequence privileges in Item_func_nextval::fix_fields(),
just like column privileges are checked in Item_field::fix_fields()
remove sequence specific hacks that kinda made sequence privilege
checks works, but not in all cases. And they were too lax,
didn't requre SELECT privilege for NEXTVAL. Also INSERT privilege looks
wrong here, UPDATE would've been more appropriate, but won't
change that for compatibility reasons.
also fixes
MDEV-36413 User without any privileges to a sequence can read from it and modify it via column default
- Added missing information about database of corresponding table for various types of commands
- Update some typos
- Reviewed by: <vicentiu@mariadb.org>