fixed view fields names check and generation (changed after Trudy review: underlying field names treat as user set ones) (BUG#7448)


mysql-test/r/view.result:
  test of view field names generation
mysql-test/t/view.test:
  test of view field names generation
sql/item.cc:
  add a flag that indicates that the name of the item was an auto-generated one and so can be changed in a view
sql/item.h:
  add a flag that indicates that the name of the item was an auto-generated one and so can be changed in a view
  layout fixed
sql/item_func.cc:
  line made less then 80 columns
sql/sql_view.cc:
  fixed checking of duplicates of view fields:
  1) case-insensitive system charset/collation is used now to compare view filds
  2) in case if the duplicate field name was of an auto-generated one, we create another unique name for it
sql/sql_yacc.yy:
  add a flag that indicates that the name of the item was an auto-generated one and so can be changed in a view