Make data frame a field of opcode_compiler_t.

This design change give me a chance to change initial data frame size
of compiled BF codes.
Added getter and setter of dataSlotCount to opcode_compiler_t.

Getter and setter of dataSlotCount are
opcode_compiler_get_data_slot_count and
opcode_compiler_set_data_slot_count respectively.

Besides, change data type of dataSlotCount from int to unsigned int.