Kludge to support building C99 mode.  This should no longer be needed
once glibc declares strcasestr by default, and not just with
-D_GNU_SOURCE.

Submitted upstream: <https://bugs.launchpad.net/hplip/+bug/1997875>

diff --git a/scan/sane/sclpml.c b/scan/sane/sclpml.c
index dc8b32ce02ad1202..f2cacd53e86800ce 100644
--- a/scan/sane/sclpml.c
+++ b/scan/sane/sclpml.c
@@ -47,6 +47,9 @@
 #define DEBUG_DECLARE_ONLY
 #include "sanei_debug.h"
 
+/* This file is not built with _GNU_SOURCE. */
+char *strcasestr(const char *, const char *);
+
 //# define  SCLPML_DEBUG
 # ifdef SCLPML_DEBUG
    # define _DBG(args...) syslog(LOG_INFO, __FILE__ " " STRINGIZE(__LINE__) ": " args)