Adds irssi perl script email_msgs.pl:

Adds irssi perl script email_msgs.pl:

This script is based on email_privmsgs.pl v0.5 from Adam James:
https://github.com/irssi/scripts.irssi.org/blob/ac4229402acecd02aad24e874316b9d2c6d1a9d2/scripts/email_privmsgs.pl

email_msgs.pl provides advanced features and customization options
in comparison to email_privmsgs.pl:
* support for public messages as well (with/without mentions);
* support for own messages as well;
* configuration options to select what messages should be emailed:
  - public received;
  - private received;
  - private sent;
  - public sent;
  - public mentions received.
* configuration option to choose whether the user must be away or not;
* configuration option to select message check/email interval;
* configuration option for the destination email address;
* configuration option to activate detailed info:
  - currently only to email the user's hostname (for spam tracking e.g.).
* fixed code warning related to hashes in original source.