add (ignored) test for floating point exception state

Thanks, @talchas!
Fix #13

tests/fpe.rs

@@ -0,0 +1,42 @@
+// This file is part of libfringe, a low-level green threading library.
+// Copyright (c) 2015, Ben Segall <talchas@gmail.com>
+// Copyright (c) 2015, edef <edef@edef.eu>
+// See the LICENSE file included in this distribution.
+#![cfg(target_os = "linux")]
+#![feature(test)]
+#![feature(thread_local)]
+#![feature(asm)]
+extern crate fringe;
+extern crate test;
+use fringe::Context;
+use test::black_box;
+
+#[thread_local]
+static mut ctx_slot: *mut Context<'static, fringe::OsStack> = 0 as *mut Context<_>;
+
+const FE_DIVBYZERO: i32 = 0x4;
+extern {
+  fn feenableexcept(except: i32) -> i32;
+}
+
+#[test]
+#[ignore]
+fn fpe() {
+  unsafe {
+    let stack = fringe::OsStack::new(4 << 20).unwrap();
+
+    let mut ctx = Context::new(stack, move || {
+        println!("it's alive!");
+        loop {
+            println!("{:?}", 1.0/black_box(0.0));
+            Context::swap(ctx_slot, ctx_slot);
+        }
+    });
+
+    ctx_slot = &mut ctx;
+
+    Context::swap(ctx_slot, ctx_slot);
+    feenableexcept(FE_DIVBYZERO);
+    Context::swap(ctx_slot, ctx_slot);
+  }
+}