Handle CGI SSL detection via HTTPS environment better. Some servers send on/off, 0/1, yes/no, and may be upper or lower case. This fix will handle all of those permutations. It was inspired by the detection done in in some other wsgi python web applications I looked at.

#!/bin/sh
# a test for issue586

hg init a
cd a
echo a > a
hg ci -Ama

hg init ../b
cd ../b
echo b > b
hg ci -Amb

hg pull -f ../a
hg merge
hg rm -f a
hg ci -Amc

hg st -A