add i_zero macro

Dockerfile

@@ -2,6 +2,11 @@ FROM quay.io/thallian/confd-env:latest
 
 RUN apk add --no-cache dovecot dovecot-ldap libressl ssmtp g++ openldap-dev dovecot-dev make tar
 
+ADD i_zero.patch /usr/include/dovecot/i_zero.patch
+WORKDIR /usr/include/dovecot
+RUN patch -p1 < i_zero.patch
+RUN rm /usr/include/dovecot/i_zero.patch
+
 RUN mkdir /tmp/pigeonhole
 RUN wget -qO- https://pigeonhole.dovecot.org/releases/2.2/dovecot-2.2-pigeonhole-0.4.18.tar.gz | tar -xz -C /tmp/pigeonhole --strip 1
 WORKDIR /tmp/pigeonhole

i_zero.patch

@@ -0,0 +1,12 @@
+diff --git a/macros.h b/macros.h
+index 566c176..ebbf480 100644
+--- a/macros.h
++++ b/macros.h
+@@ -240,4 +240,7 @@
+ #  define STATIC_ARRAY
+ #endif
+
++#define i_zero(p) memset(p, 0, sizeof(*(p)))
++#define i_zero_safe(p) safe_memset(p, 0, sizeof(*(p)))
++
+ #endif