Upgrade to latest rust (DANGEROUS)

Closes #76

Notice the transmute is replaced by direct casting by pointers. I do
not know how this affects the usage of the library. I left the ‘unused
import’ warning on in case this can be fixed later. If this is
critical, I would recommend doing an analysis and document which uses
cases one should be careful.

Conflicts:
	src/gen/main.rs

Author: bvssvni

src/gen/main.rs

@@ -286,7 +286,7 @@ impl<'a, W: Writer> Generator<'a, W> {
         self.write_line("    pub fn new(ptr: Option<extern \"system\" fn()>, failing_fn: F) -> FnPtr<F> {");
         self.write_line("        use std::mem::transmute;");
         self.write_line("        match ptr {");
-        self.write_line("            std::option::Some(p) => FnPtr { f: unsafe { transmute(p) }, is_loaded: true },");
+        self.write_line("            std::option::Some(p) => FnPtr { f: unsafe { std::ptr::read(&p as *_ as *F) }, is_loaded: true },");
         self.write_line("            None => FnPtr { f: failing_fn, is_loaded: false },");
         self.write_line("        }");
         self.write_line("    }");