Suggestion: Describe in Gnus manuall on how to allow multiple IMAP accounts in same server

[CHENG Gao]

It's not clear in Gnus manual how to use multiple accounts in same IMAP
server. My company emails are hosted by virtual hosting server, and I
have my personal account while at the same time I need read some common
email accounts. I think it's common for many users.

I struggled for some time and found the solution.

Say nnimap address is imap.mysite.com
Two accounts: one@mysite.com & other@mysite.com

Two .authinfo files are needed to seperate the auth otherwise only the
first one with imap address imap.mysite.com is used for authentication
of both accounts.

So the setting should be:
        (nnimap "one-mysite"
                     (nnimap-server-port 143)
                     (nnimap-address "imap.mysite.com")
                     (nnimap-list-pattern ("INBOX" "mail/*"))
                     (nnimap-authinfo-file "~/.emacs.d/.authinfo"))
        (nnimap "other-mysite"
                     (nnimap-server-port 143)
                     (nnimap-address "imap.mysite.com")
                     (nnimap-list-pattern ("INBOX" "mail/*"))
                     (nnimap-authinfo-file "~/.emacs.d/.authinfo2"))

I think I need not bother to demonstrate two .authinfo files here.

The right location to add this is `nnimap-authinfo-file under "6.5 IMAP"
in Gnus manual, something like:

If you have more than one account under same IMAP server, you need use
one .authinfo for each account, and explicitly configure each imap
account to point to them. blah blah