Replace try! with ?

`?` was stabilised in `1.13`, which is already below the minimum
required Rust version.

This gets rid of deprecation warnings.

src/os/unix/mod.rs

@@ -118,7 +118,7 @@ impl Library {
     where P: AsRef<OsStr> {
         let filename = match filename {
             None => None,
-            Some(ref f) => Some(try!(cstr_cow_from_bytes(f.as_ref().as_bytes()))),
+            Some(ref f) => Some(cstr_cow_from_bytes(f.as_ref().as_bytes())?),
         };
         with_dlerror(move || {
             let result = unsafe {
@@ -149,7 +149,7 @@ impl Library {
     where F: FnOnce() -> ::Result<Symbol<T>>
     {
         ensure_compatible_types::<T, *mut raw::c_void>();
-        let symbol = try!(cstr_cow_from_bytes(symbol));
+        let symbol = cstr_cow_from_bytes(symbol)?;
         // `dlsym` may return nullptr in two cases: when a symbol genuinely points to a null
         // pointer or the symbol cannot be found. In order to detect this case a double dlerror
         // pattern must be used, which is, sadly, a little bit racy.

src/os/windows/mod.rs

@@ -73,7 +73,7 @@ impl Library {
     /// definied behaviour.
     pub unsafe fn get<T>(&self, symbol: &[u8]) -> ::Result<Symbol<T>> {
         ensure_compatible_types::<T, FARPROC>();
-        let symbol = try!(cstr_cow_from_bytes(symbol));
+        let symbol = cstr_cow_from_bytes(symbol)?;
         with_get_last_error(|| {
             let symbol = libloaderapi::GetProcAddress(self.0, symbol.as_ptr());
             if symbol.is_null() {

src/util.rs

@@ -42,9 +42,9 @@ pub fn cstr_cow_from_bytes<'a>(slice: &'a [u8]) -> Result<Cow<'a, CStr>, NullErr
         // Slice out of 0 elements
         None => unsafe { Cow::Borrowed(CStr::from_ptr(&ZERO)) },
         // Slice with trailing 0
-        Some(&0) => Cow::Borrowed(try!(CStr::from_bytes_with_nul(slice))),
+        Some(&0) => Cow::Borrowed(CStr::from_bytes_with_nul(slice)?),
         // Slice with no trailing 0
-        Some(_) => Cow::Owned(try!(CString::new(slice))),
+        Some(_) => Cow::Owned(CString::new(slice)?),
     })
 }