libwebsockets

format strings: ban %.*s as some platforms lack it

The %.*s is very handy to print strings where you have a length, but
there is no NUL termination.  It's quite widely supported but at least
one vendor RTOS toolchain doesn't have it.

Since there aren't that many uses of it yet, audit all uses and
convert to a new helper lws_strnncpy() which uses the smaller of
two lengths.