set_contact
Description:
Sets this to point to one of contact's e-mail addresses indicated by email_num.
Parameters:
| this | an Destination | 
| contact | an Contact | 
| email_num | an email index | 
Sets this to point to one of contact's e-mail addresses indicated by email_num.
| this | an Destination | 
| contact | an Contact | 
| email_num | an email index |