runtime: increase stack system space on windows/amd64
runtime: increase stack system space on windows/amd64

gotest src/pkg/exp/template/html was crashing because the exception handler overflowed the goroutine stack.

R=alex.brainman, golang-dev
CC=golang-dev
http://codereview.appspot.com/5031049

Committer: Alex Brainman <54ba58c8441b5eff861de6b4e5ee46baf086b142@gmail.com>

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