SHOW FIELDS FROM a view with no valid definer was possible (since fix
for Bug#26817), but gave NULL as a field-type. This led to mysqldump-ing
of such views being successful, but loading such a dump with the client
failing. Patch allows SHOW FIELDS to give data-type of field in underlying
table.


mysql-test/r/information_schema_db.result:
  Fix test results: SHOW FIELDS FROM a view with no valid DEFINER
  gives us the field-type of the underlying table now rather than NULL.
sql/sql_base.cc:
  In the case of SHOW FIELDS FROM <view>, do not require a valid
  DEFINER for determining underlying data-type like we usually do.
  This is needed for mysqldump.