Fix crash in mysqldump -c triggered by tables with a large number of long

field names. (Bug #10286)


client/mysqldump.c:
  Use a DYNAMIC_STRING for the 'INSERT ...' pattern so we can handle
  an arbitrary number of fields. Also rename the internal cFlag to 
  opt_complete_insert so it is clear what it does.
mysql-test/t/mysqldump.test:
  Add regression test for 10286
mysql-test/r/mysqldump.result:
  Update results