Throw openssl dependency away

[dndx]

@clowwindy @madeye

RC4 have a very simple algorithm and can be implemented in just few lines of code. According to my test, we only need the EVP_BytesToKey(3) to make password derivation. It seems that EVP_BytesToKey(3) is using PKCS#5 v1.5 so it's possible just implement this algorithm and throw openssl dependency away.

In my encrypt.c , I just used EVP_BytesToKey(3) to do derivation. After that I used a rc4 implementation I found in OpenBSD Directory and it's working very well.