Version for 4.0. Committed for merge.
If the result table is one of the select tables in INSERT SELECT,
we must not disable the result tables indexes before selecting.
mysql_execute_command() detects the match for other reasons and
adds the flag OPTION_BUFFER_RESULT to the 'select_options'. 
In this case the result is put into a temporary table first. 
Hence, we can defer the preparation of the insert
table until the result is to be used.


mysql-test/r/insert_select.result:
  BUG#6034 - Error code 124:  Wrong medium type.
  The test results.
mysql-test/t/insert_select.test:
  BUG#6034 - Error code 124:  Wrong medium type.
  The test case.
sql/sql_select.cc:
  BUG#6034 - Error code 124:  Wrong medium type.
  With OPTION_BUFFER_RESULT in the 'select_options',
  defer the preparation of the insert table until the 
  result is to be used. Unfortunately, this happens
  at several places.