Code cleanups during code reviews

Ensure we get error if INSERT IGNORE ... SELECT fails
Fixed wrong key_part->key_length usage in index_merge


client/mysql.cc:
  Code cleanups & simply optimizations
mysql-test/r/information_schema.result:
  Safety
mysql-test/t/information_schema.test:
  Safety
sql/ha_ndbcluster.cc:
  Code cleanups
sql/item.cc:
  Code cleanups
sql/item_subselect.cc:
  Code cleanups
sql/item_sum.cc:
  Code cleanups
sql/opt_range.cc:
  Made get_index_only_read_time() static (instad of inline) to increase portability (function was not declared before use)
  Simple optimization
  Fixed wrong key_part->key_length usage in index_merge
  Removed not used variable n_used_covered
  Indentation fixes & comment cleanups
sql/parse_file.cc:
  Code cleanups
sql/sql_base.cc:
  Code cleanups
sql/sql_bitmap.h:
  Added missing return
sql/sql_insert.cc:
  Ensure we get error if INSERT IGNORE ... SELECT fails
sql/sql_select.cc:
  Code cleanups
sql/sql_show.cc:
  Safety fix if a LOT of errors are ignored
sql/sql_update.cc:
  Code cleanups
sql/table.cc:
  Code cleanups
sql/table.h:
  Code cleanups
sql/uniques.cc:
  Code cleanups
strings/decimal.c:
  Simple optimization
  Code cleanups

mysql-test/r/information_schema.result

@@ -1,3 +1,4 @@
+DROP TABLE IF EXISTS t0,t1,t2;
 show variables where variable_name like "skip_show_database";
 Variable_name	Value
 skip_show_database	OFF

mysql-test/t/information_schema.test

@@ -4,6 +4,11 @@
 # Test for information_schema.schemata &
 # show databases
 
+--disable_warnings
+DROP TABLE IF EXISTS t0,t1,t2;
+--enable_warnings
+
+
 show variables where variable_name like "skip_show_database";
 grant select, update, execute on test.* to mysqltest_2@localhost;
 grant select, update on test.* to mysqltest_1@localhost;