syntax error detection added
duplication definition error report added No.2
undefined error detection add No.3
uselist symbol not used error detection added. No.7
symbol not used in symbolTable error detection. No4
relAddress too big error detection added. No5
extaddr exceeds uselist length error detection added. No.7
absolute address and relative address overflow errors detection added. No.8 & No.9
illegal immediate instr and illegal opcode instr error detection added No.10 & No.11