+PH/12 Installed Andrey Panin's patch to add a dovecot authenticator. Various
+ tweaks were necessary in order to get it to work:
+ (a) The code assumed that strncpy() returns a negative number on buffer
+ overflow, which isn't the case. Replaced with Exim's string_format()
+ function.
+ (b) There were several signed/unsigned issues. I just did the minimum
+ hacking in of casts. There is scope for a larger refactoring.
+ (c) The code used strcasecmp() which is not a standard C function.
+ Replaced with Exim's strcmpic() function.
+ (d) The code set only $1; it now sets $auth1 as well.
+ (e) A simple test gave the error "authentication client didn't specify
+ service in request". It would seem that Dovecot has changed its
+ interface. Fortunately there's a specification; I followed it and
+ changed what the client sends and it appears to be working now.
+