Fix build with upcoming rust 1.36.

found by semarie@ in
https://reviews.freebsd.org/D20810#change-K68aYoUXfAu1, regression in
rust itself tracked in rust-lang/rust#62301

Builds fine with rust 1.35.

www/tor-browser/browser/Makefile

@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile,v 1.33 2019/06/25 20:25:23 sthen Exp $
+# $OpenBSD: Makefile,v 1.34 2019/07/02 16:52:09 landry Exp $
 # Some of this comes from www/firefox-esr as apropos, since Tor
 # browser is a fork of ESR.  It is a good idea to look at that
 # Makefile when editing this one (ESR versions not always the same).
@@ -15,7 +15,7 @@ PATCHORIG =		.pat.orig
 
 PKGNAME =		${TB_PREFIX}-browser-${TB_VERSION}
 DISTNAME =		${BROWSER_NAME}-${TB_VERSION}
-REVISION =		0
+REVISION =		1
 
 SO_VERSION =		4.0
 MOZILLA_LIBS =		xul clearkey lgpllibs mozavcodec mozavutil mozgtk

www/tor-browser/browser/patches/patch-servo_components_style_build_gecko_rs

@@ -0,0 +1,23 @@
+$OpenBSD: patch-servo_components_style_build_gecko_rs,v 1.1 2019/07/02 16:52:09 landry Exp $
+
+Fix build with rust 1.36.
+
+Index: servo/components/style/build_gecko.rs
+--- servo/components/style/build_gecko.rs.orig
++++ servo/components/style/build_gecko.rs
+@@ -36,6 +36,7 @@ mod bindings {
+     use std::fs::{self, File};
+     use std::io::{Read, Write};
+     use std::path::{Path, PathBuf};
++    use std::panic::UnwindSafe;
+     use std::process::{Command, exit};
+     use std::slice;
+     use std::sync::Mutex;
+@@ -384,6 +385,7 @@ mod bindings {
+     fn generate_structs() {
+         #[derive(Debug)]
+         struct Callbacks(HashMap<String, RegexSet>);
++        impl UnwindSafe for Callbacks {}
+         impl ParseCallbacks for Callbacks {
+             fn enum_variant_behavior(&self,
+                                      enum_name: Option<&str>,