Update to libpcap 1.9.1 (initial commit, no Nmap-specific patches)

libpcap/missing/win_snprintf.c

@@ -1,6 +1,8 @@
 #include <stdio.h>
 #include <stdarg.h>
 
+#include "portability.h"
+
 int
 pcap_vsnprintf(char *str, size_t str_size, const char *format, va_list args)
 {
@@ -13,6 +15,16 @@ pcap_vsnprintf(char *str, size_t str_size, const char *format, va_list args)
 	 * that str is null-terminated, but C99's vsnprintf()
 	 * and snprintf() do, and we want to offer C99 behavior,
 	 * so forcibly null-terminate the string.
+	 *
+	 * We don't, however, offer C99 behavior for the return
+	 * value; _vsnprintf_s() returns -1, not the number of
+	 * characters that would have been put into the buffer
+	 * had it been large enough, if the string is truncated.
+	 * The only way to get that value is to use _vscprintf();
+	 * getting that count isn't worth the re-formatting.
+	 *
+	 * XXX - does _vsnprintf_s() return -1 on a formatting
+	 * error?
 	 */
 	str[str_size - 1] = '\0';
 	return (ret);