Most "new" failures fixed in the following files:
- sql_select.cc
- item.cc
- item_func.cc
- opt_subselect.cc
Other things:
- Allocate udf_handler strings in mem_root
- Required changes in sql_string.h
- Add mem_root as argument to some new [] calls
- Mark udf_handler strings as thread specific
- Removed some comment blocks with code
TVC can be used in UNION-statement, in view and in subquery.
Files where TVC is defined and its methods are stored added.
Methods exec and prepare for TVC added.
Tests for TVC added.
