Point to GitHub for the pcapng specification.

Change-Id: I33faa41e8b0f36ee49d29fe391feafd94d0a7e80
Reviewed-on: https://code.wireshark.org/review/10245
Reviewed-by: Guy Harris <guy@alum.mit.edu>

docbook/wsug_src/WSUG_app_files.asciidoc

@@ -16,7 +16,7 @@ are saved to a capture file, it's helpful to know a bit about the capture file
 contents.
 
 Wireshark uses the
-link:https://www.winpcap.org/ntar/draft/PCAP-DumpFileFormat.html[pcapng] file
+link:https://github.com/pcapng/pcapng[pcapng] file
 format as the default format to save captured packets. It is very flexible
 but other tools may not support it.
 

epan/dissectors/file-pcapng.c

@@ -1,6 +1,6 @@
 /* file-pcapng.c
  * Routines for PCAPNG File Format
- * http://www.winpcap.org/ntar/draft/PCAP-DumpFileFormat.html
+ * https://github.com/pcapng/pcapng
  *
  * Copyright 2015, Michal Labedzki for Tieto Corporation
  *

wiretap/pcapng.c

@@ -21,9 +21,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-/* File format reference:
- *   https://www.winpcap.org/ntar/draft/PCAP-DumpFileFormat.html
- * File format specification:
+/* File format specification:
  *   https://github.com/pcapng/pcapng
  * Related Wiki page:
  *   https://wiki.wireshark.org/Development/PcapNg