imap.h: Corrected incorrect comment clarification

   struct */

struct imap_conn {

  struct pingpong pp;

  char *mailbox;          /* Message ID to fetch */

  char *mailbox;          /* Mailbox to select */

  unsigned int authmechs; /* Accepted authentication mechanisms */

  unsigned int authused;  /* Auth mechanism used for the connection */

  imapstate state;        /* Always use imap.c:state() to change state! */