news: Raise the limit for "number of times" from 127 to 65535

news: Raise the limit for "number of times" from 127 to 65535

News reporting merges news items into recent items with same contents,
until their count reaches 127.  Raise that limit to 65535, by making
struct nwsstr member nws_ntm unsigned short.  Size of struct nwsstr
stays the same on all common machines.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>