[core] proxy_create_env() tweaks
[core] proxy_create_env() tweaks

reorder some code for better asm

proxy_set_Forwarded() sets multiple request headers, and does so prior
to walking all request headers to create request to backend.  This is
done so that specific already-existing request headers from client are
overwritten (intentionally) in proxy_set_Forwarded().

Expect header is handled, but not expected since client-sent Expect
header is handled (and unset) in connection_handle_read_post_state()

gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4