Describe size for var structure of block type.
* A variable should have an unique name in the function
* A variable is represented by a structure of type `MIR_var_t`
* The structure contains variable name and its type
+ * The structure contains also type size for variable of `MIR_T_BLK` type
* MIR function with its arguments is created through API function `MIR_item_t MIR_new_func (MIR_context_t ctx, const
char *name, size_t nres, MIR_type_t *res_types, size_t nargs, ...)`
or function `MIR_item_t MIR_new_func_arr (MIR_context_t ctx, const char *name, size_t nres, MIR_type_t *res_types, size_t nargs, MIR_var_t *arg_vars)`
