In ROW_FORMAT=DYNAMIC and ROW_FORMAT=COMPRESSED, column prefix indexes
require that prefixes of externally stored columns be written to the
undo log. This may make the undo log record bigger than the record on
the B-tree page.  The maximum size of an undo log record is the page
size.  That must be checked for, in dict_index_add_to_cache().

dict_index_add_to_cache(): Skip the undo log size check for REDUNDANT
and COMPACT tables. These tables store prefixes of externally stored
columns locally within the clustered index record.  There are no special
considerations for the undo log record size.

innodb-index.test: Ensure that the check exists for ROW_FORMAT=DYNAMIC,
but not for ROW_FORMAT=COMPACT.

This fixes issue #99.  rb://28 approved by Sunny.