- Changed Cached_item_field not copy data for fields with NULL value
- In key_copy() and key_restore() don't copy data for fields with NULL value

Fixed code to avoid valgrind warnings
- Use c_ptr_safe instead of c_ptr()

Removed "QQ" from comments (QQ was ment to be used for internal comments that should be removed before pushing)
Fixed wrong alias used (from previous patch)


sql/event_db_repository.cc:
  Update testing if event table is valid (to avoid valgrind errors)
sql/ha_partition.cc:
  m_ordered_scan_ongoing was not initialized
  Reset null bits in record to avoid valgrind errors
sql/handler.h:
  Added flag if storage engine will write row verbatim and the row contains varchar or null fields
  (in which case we must clear the row to avoid valgrind warnings)
sql/item_buff.cc:
  Changed Cached_item_field not copy data for fields with NULL value
  (Optimization and avoids valgrind warnings)
sql/item_func.cc:
  c_ptr() -> c_ptr_safe()
sql/key.cc:
  In key_copy() and key_restore() don't copy data for fields with NULL value
sql/opt_range.cc:
  c_ptr() -> c_ptr_safe()
sql/sql_base.cc:
  Added TRASH() to table->record[0] to find out if we access not initialzed data.
  Initialize null_bytes to:
  - Get consistent tests
  - Ensure we don't get valgrind warnings for null fields (as we may only update a couple of bits in a byte)
sql/sql_class.cc:
  Removed "QQ" from comments
sql/sql_insert.cc:
  Initialize row to default values if we are using valgrind and row will be copied verbatim to disk in storage engine.
sql/sql_load.cc:
  QQ -> TODO
sql/sql_parse.cc:
  Removed old not used code marked QQ and withing "#ifdef REMOVED"
sql/sql_select.cc:
  QQ -> TODO
  Initialize some variables that was used uninitialized
  Added DBUG_ASSERT() to find out if thd was not properly initialized for sub queries
sql/sql_test.cc:
  Fixed format for printing to DBUG file
  Fixed wrong alias used (from previous patch)
sql/sql_trigger.h:
  QQ -> TODO
sql/table.cc:
  QQ -> TODO
storage/maria/ha_maria.cc:
  Mark table with HA_RECORD_MUST_BE_CLEAN_ON_WRITE, if row is written verbatim to disk and contains varchar or null fields.
storage/maria/ma_open.c:
  Added flags if table has varchar or null fields
storage/maria/maria_def.h:
  Added flags if table has varchar or null fields
storage/myisam/ha_myisam.cc:
  Mark table with HA_RECORD_MUST_BE_CLEAN_ON_WRITE, if row is written verbatim to disk and contains varchar or null fields.
storage/myisam/mi_open.c:
  Fixed memory overrun bug when using fulltext keys
storage/xtradb/row/row0sel.c:
  Removed initialization of null bits. (not needed anymore)