gnu: mailutils: Look up Scheme variables in the right module.

Fixes <https://issues.guix.gnu.org/49295>.
Reported by Maxime Devos <maximedevos@telenet.be>.

* gnu/packages/patches/mailutils-variable-lookup.patch: New file.
* gnu/packages/mail.scm (mailutils)[source]: Use it.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -1435,6 +1435,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/luit-posix.patch				\
   %D%/packages/patches/lvm2-static-link.patch			\
   %D%/packages/patches/mailutils-fix-uninitialized-variable.patch	\
+  %D%/packages/patches/mailutils-variable-lookup.patch		\
   %D%/packages/patches/make-impure-dirs.patch			\
   %D%/packages/patches/marble-qt-add-qt-headers.patch		\
   %D%/packages/patches/mariadb-CVE-2021-27928.patch		\

gnu/packages/mail.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014, 2015, 2017, 2020 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2014 Ian Denhardt <ian@zenhack.net>
 ;;; Copyright © 2014 Sou Bunnbu <iyzsong@gmail.com>
@@ -269,7 +269,8 @@ example, modify the message headers or body, or encrypt or sign the message.")
                "17smrxjdgbbzbzakik30vj46q4iib85ksqhb82jr4vjp57akszh9"))
              (patches
               ;; Fixes https://issues.guix.gnu.org/43088.
-              (search-patches "mailutils-fix-uninitialized-variable.patch"))))
+              (search-patches "mailutils-fix-uninitialized-variable.patch"
+                              "mailutils-variable-lookup.patch"))))
     (build-system gnu-build-system)
     (arguments
      `(#:phases

gnu/packages/patches/mailutils-variable-lookup.patch

@@ -0,0 +1,26 @@
+Have 'send-message' look up 'mu-debug' & co. in the right
+module: <https://issues.guix.gnu.org/49968>.
+
+Submitted: https://lists.gnu.org/archive/html/bug-mailutils/2021-09/msg00000.html
+
+---
+ include/mailutils/guile.h | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/include/mailutils/guile.h b/include/mailutils/guile.h
+index f05550678..47f89db39 100644
+--- a/include/mailutils/guile.h
++++ b/include/mailutils/guile.h
+@@ -20,7 +20,8 @@
+ 
+ #include <libguile.h>
+ 
+-#define MU_SCM_SYMBOL_VALUE(p) SCM_VARIABLE_REF(scm_c_lookup(p))
++#define MU_SCM_SYMBOL_VALUE(p)			\
++  (scm_c_public_ref ("mailutils mailutils", p))
+ 
+ typedef struct
+ {
+-- 
+2.33.0
+