mcabber uses HAVE_SNPRINTF throughout the code but its configure script actually never checks for it

--- configure
+++ configure
@@ -5462,6 +5462,7 @@
 for ac_func in alarm arc4random bzero gethostbyname gethostname inet_ntoa \
                 isascii memmove memset modf select setlocale socket strcasecmp \
                 strchr strdup strncasecmp strrchr strstr strcasestr vsnprintf \
+                snprintf \
                 iswblank
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
--- config.h.in
+++ config.h.in
@@ -246,6 +246,9 @@
 /* Define to 1 if you have the `vprintf' function. */
 #undef HAVE_VPRINTF
 
+/* Define to 1 if you have the `snprintf' function. */
+#undef HAVE_SNPRINTF
+
 /* Define to 1 if you have the `vsnprintf' function. */
 #undef HAVE_VSNPRINTF