Mail: fixed handling of AF_UNIX addresses in "listen".

This makes AF_UNIX addresses in mail officially supported.
diff --git a/src/mail/ngx_mail.c b/src/mail/ngx_mail.c
index b097778..3812e15 100644
--- a/src/mail/ngx_mail.c
+++ b/src/mail/ngx_mail.c
@@ -263,6 +263,12 @@
         break;
 #endif
 
+#if (NGX_HAVE_UNIX_DOMAIN)
+    case AF_UNIX:
+        p = 0;
+        break;
+#endif
+
     default: /* AF_INET */
         sin = (struct sockaddr_in *) sa;
         p = sin->sin_port;
diff --git a/src/mail/ngx_mail_core_module.c b/src/mail/ngx_mail_core_module.c
index ecb7229..86d0b3b 100644
--- a/src/mail/ngx_mail_core_module.c
+++ b/src/mail/ngx_mail_core_module.c
@@ -340,6 +340,14 @@
             break;
 #endif
 
+#if (NGX_HAVE_UNIX_DOMAIN)
+        case AF_UNIX:
+            off = offsetof(struct sockaddr_un, sun_path);
+            len = sizeof(((struct sockaddr_un *) sa)->sun_path);
+            port = 0;
+            break;
+#endif
+
         default: /* AF_INET */
             off = offsetof(struct sockaddr_in, sin_addr);
             len = 4;