added test for C99 vsnprintf

configure.in

@@ -103,6 +103,32 @@ AC_FUNC_ALLOCA
 AC_CHECK_FUNCS(gethostname select poll strerror strcasecmp strncasecmp setpgid atexit mallinfo snprintf vsnprintf asprintf vasprintf mkstemp)
 
 
+dnl ripped from samba
+dnl 
+C_CACHE_CHECK([for C99 vsnprintf],_cv_HAVE_C99_VSNPRINTF,[
+AC_TRY_RUN([
+#include <sys/types.h>
+#include <stdarg.h>
+void foo(const char *format, ...) { 
+       va_list ap;
+       int len;
+       char buf[5];
+
+       va_start(ap, format);
+       len = vsnprintf(0, 0, format, ap);
+       va_end(ap);
+       if (len != 5) exit(1);
+
+       if (snprintf(buf, 3, "hello") != 5 || strcmp(buf, "he") != 0) exit(1);
+
+       exit(0);
+}
+main() { foo("hello"); }
+],
+_cv_HAVE_C99_VSNPRINTF=yes,_cv_HAVE_C99_VSNPRINTF=no,_cv_HAVE_C99_VSNPRINTF=cross)])
+if test x"$_cv_HAVE_C99_VSNPRINTF" = x"yes"; then
+    AC_DEFINE(HAVE_C99_VSNPRINTF)
+fi
 
 dnl Loading of dynamic libraries at runtime
 dnl =======================================