net/http/cgi: make tests compile on plan9

Don't reference the non-portable syscall.Signal(0).

Maybe they'll pass too. Untested. plan9 bit from
Akshat Kumar.

R=golang-dev, akumar
CC=golang-dev
https://codereview.appspot.com/7370049
doc: fix wiki codelab description of template parsing

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/7372048