doc/go1.8: support "option ndots:0" in resolv.conf

Updates #15419.

Change-Id: If7c80adcb38b5731e337b2ae2d9d76fcf8513d8e
Reviewed-on: https://go-review.googlesource.com/27271Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.8.txt

+Tools:
+
+Ports:
+
+API additions and behavior changes:
+
+net: support "option ndots:0" in resolv.conf (CL 24901)