Patch from Debian: "use system djvu", see
https://sources.debian.org/patches/k2pdfopt/2.55%2Bds-2/0010-willuslib-use-system-djvu.patch/

Index: willuslib/bmpdjvu.c
--- willuslib/bmpdjvu.c.orig
+++ willuslib/bmpdjvu.c
@@ -23,7 +23,7 @@
 #include "willus.h"
 
 #ifdef HAVE_DJVU_LIB
-#include <djvu.h>
+#include <libdjvu/ddjvuapi.h>
 
 static void handle(int wait,ddjvu_context_t *ctx);
 static void djvu_add_page_info(char *buf,ddjvu_document_t *doc,int page,int npages);
