Fix a few general mistakes in the program

[colfrog]

• Mutexes aren't necessary because read/writes are asynchronous
• Sanitize some configuration checks
• Use getenv for the config
• Fix a few segmentation faults and double frees
• Fix GNUTLS permission denied error in irc_encrypt_connection

With this patch the client connects to Snoonet using the default configuration.

[rkitover]

Will merge from #13.