mu_str_to_c test fails (endianness problem)

Have a user report for failing mu_str_to_c test on sparc64 for
mailutils-3.4:

The error is obviously a big endian problem:

#                             -*- compilation -*-
1. strtoc.at:17: testing mu_str_to_c ...
./strtoc.at:18: strtoc
--- /dev/null   2018-05-03 08:45:02.879999416 +0200
+++ /var/tmp/portage/net-mail/mailutils-3.4/work/mailutils-3.4/libmailutils/tests/testsuite.dir/at-groups/1/stderr      2018-05-04 07:51:41.401805688 +0200
@@ -0,0 +1 @@
+14: FAIL: mu_c_cidr value differ: expected: 127.0.0.0/255.0.0.0, but got: 0.0.0.127/255.0.0.0
./strtoc.at:18: exit code was 1, expected 0
1. strtoc.at:17: 1. mu_str_to_c (strtoc.at:17): FAILED (strtoc.at:18)

-- 
Eray