[c] 패스워드 암호화/사용자 정보 보기

## Function

  Program passwd.c is a program for password encryption.

## The following is the execution examples.

$ ./passwd

Usage : ./passwd real_password [crypted_password]

$ ./passwd anypasswordstring

saltc = aC

aCe0DjjrqnxcA

$ ./passwd anypasswordstring aCe0DjjrqnxcA 

Password is Good.

$ ./passwd anypasswordstring aCe0Djjrqnxc

Password is Bad.