erroneous check

Problem: Actually there were two problems in the server code. The check
for SQLCOM_FLUSH in SF/Triggers were not according to the existing
architecture which uses sp_get_flags_for_command() from sp_head.cc .
This function was also missing a check for SQLCOM_FLUSH which has a
problem combined with prelocking. This changeset fixes both of these
deficiencies as well as the erroneous check in
sp_head::is_not_allowed_in_function() which was a copy&paste error.


mysql-test/r/sp-error.result:
  update result
mysql-test/r/trigger.result:
  update result
mysql-test/t/sp-error.test:
  FLUSH can create a problem with prelocking, hence it's disabled.
  There is a better way to check this than a check in the parser.
  Now we use sp_get_flags_for_command() and the error returned is
  different.
mysql-test/t/trigger.test:
  FLUSH can create a problem with prelocking, hence it's disabled.
  There is a better way to check this than a check in the parser.
  Now we use sp_get_flags_for_command() and the error returned is
  different.
sql/sp_head.cc:
  FLUSH and RESET are not allowed inside a SF/Trigger.
  Because they don't imply a COMMIT sp_head::HAS_COMMIT_OR_ROLLBACK
  cannot be used. Two new flags were introduced for that reason.
sql/sp_head.h:
  Don't check m_type as this check is erroneous. This is probably
  a copy and paste error when moving code from somewhere else. Another
  fact which supports this was prefixing the enum value with the name
  of class sp_head.
  
  Adding two new flags HAS_SQLCOM_RESET and HAS_SQLCOM_FLUSH. The values
  are 2048 and 4096 because in the 5.1 branch there are already new flags
  which are with values up-to 1024.
sql/sql_parse.cc:
  FLUSH can cause a problem with prelocking in SF/Trigger and
  therefore is already disabled. RESET is also disabled because
  is handled by the same code as FLUSH. We won't allow RESET inside
  SF/Trigger at that stage without thorough analysis. The check for
  them is already done in the parser by calling
  is_not_allowed_in_function()
sql/sql_yacc.yy:
  By listing SQLCOM_FLUSH as command which implies COMMIT
  in sp_get_flags_for_command() the check in sql_yacc.yy is
  obsolete.