Mail: mail dependencies are now honored while building addons.

auto/modules

diff --git a/auto/modules b/auto/modules
index 3feaf53..e1eda94 100644
--- a/auto/modules
+++ b/auto/modules
@@ -483,6 +483,8 @@
 
     modules="$modules $MAIL_PROXY_MODULE"
     MAIL_SRCS="$MAIL_SRCS $MAIL_PROXY_SRCS"
+
+    NGX_ADDON_DEPS="$NGX_ADDON_DEPS \$(MAIL_DEPS)"
 fi