Revert "Use dwarf exceptions on i686 as well"

This reverts commit ca43ab5ccd.

It was reported in https://github.com/mstorsjo/llvm-mingw/issues/8 that
the dwarf unwinding on i686 doesn't always work.

This commit adds a testcase for the case that didn't work previously.

test/exception-locale.cpp

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2018 SquallATF
+ *
+ * This file is part of llvm-mingw.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <iostream>
+#include <typeinfo>
+
+int main(int argc, char *argv[]) {
+    try {
+        std::locale loc("test");
+    } catch (std::runtime_error& e) {
+        std::cerr << "Caught " << e.what() << std::endl;
+        std::cerr << "Type " << typeid(e).name() << std::endl;
+    } catch (...) {
+        std::cerr << "catch all" << std::endl;
+    }
+
+    return 0;
+}