r17792: io.out.winsserver is a const char *,

r17792: io.out.winsserver is a const char *,
and iname->winserver = talloc_steal(iname, io.out.winsserver)
generated a warning, so I changed iname->winsserver to also
be a const char *.

then a talloc_free(iname->winsserver) would generate a warning,
but we can steal it into the tmp_ctx without a warning
and that gets free'ed a few lines later.

metze
(This used to be commit fdef17f81e5fc48cca3dd7611d6d5007147473b1)