gphoto2: fix libgphoto2 logging integration

In libgphoto2-2.5.0 (tagged for release on 2012-07-10) the GPLogFunc no
longer takes a va_list.  Instead, it passes a formatted message.

acinclude.m4

@@ -431,6 +431,10 @@ AC_DEFUN([SANE_CHECK_GPHOTO2],
         GPHOTO2_LIBS="" 
       else
         SANE_EXTRACT_LDFLAGS(GPHOTO2_LIBS, GPHOTO2_LDFLAGS)
+        if pkg-config --atleast-version=2.5.0 libgphoto2; then
+          AC_DEFINE([GPLOGFUNC_NO_VARGS], [1],
+                    [Define if GPLogFunc does not take a va_list.])
+        fi
       fi
     fi
   fi

backend/gphoto2.c

@@ -353,14 +353,23 @@ static const SANE_Device *devlist[] = {
  * debug_func - called for gphoto2 debugging output (if enabled)
  */
 static void
+#ifdef GPLOGFUNC_NO_VARGS
+debug_func (GPLogLevel level, const char *domain, const char *message,
+            void __sane_unused__ * data)
+#else
 debug_func (GPLogLevel level, const char *domain, const char *format,
 	    va_list args, void __sane_unused__ * data)
+#endif
 {
   if (level == GP_LOG_ERROR)
     DBG (0, "%s(ERROR): ", domain);
   else
     DBG (0, "%s(%i): ", domain, level);
+#ifdef GPLOGFUNC_NO_VARGS
+  DBG (0, "%s", message);
+#else
   sanei_debug_msg (0, DBG_LEVEL, STRINGIFY (BACKEND_NAME), format, args);
+#endif
   DBG (0, "\n");
 }
 

configure

@@ -17230,6 +17230,11 @@ done
      unset tmp_LIBS
      unset param
 
+        if pkg-config --atleast-version=2.5.0 libgphoto2; then
+
+$as_echo "#define GPLOGFUNC_NO_VARGS 1" >>confdefs.h
+
+        fi
       fi
     fi
   fi

include/sane/config.h.in

@@ -21,6 +21,9 @@
    language is requested. */
 #undef ENABLE_NLS
 
+/* Define if GPLogFunc does not take a va_list. */
+#undef GPLOGFUNC_NO_VARGS
+
 /* Define to 1 if struct sockaddr_storage has an ss_family member */
 #undef HAS_SS_FAMILY