glibc-fix.diff:
--- qpopper4.1.0/popper/popper.h.orig	2011-05-30 21:13:40.000000000 +0200
+++ qpopper4.1.0/popper/popper.h	2016-12-31 09:31:26.910604367 +0100
@@ -313,7 +313,7 @@
 #if !( defined(BSD) && (BSD >= 199306) ) && !defined(__USE_BSD)
    extern int              sys_nerr;
 #  ifndef FREEBSD
-     extern char         *   sys_errlist[];
+     extern const char         * const  sys_errlist[];
 #    ifndef SYS_SIGLIST_DECLARED
 #      ifndef __linux__
          extern char         *   sys_siglist[];
