Prevent HTTPoxy attack (CVE-2016-1000110)

Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which
indicates that the script is in CGI mode.

Issue reported and patch contributed by Rémi Rampin.
diff --git a/Misc/ACKS b/Misc/ACKS
index 7aa8fc8..0210a4c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1123,6 +1123,7 @@
 Jeff Ramnani
 Varpu Rantala
 Brodie Rao
+Rémi Rampin
 Senko Rasic
 Antti Rasinen
 Nikolaus Rath