rust/lua: add method for pushing bytes

Much like pushstring, but accepts an &[u8] as an argument instead of an &str.

In support of ticket #8533.

rust/src/lua.rs

@@ -57,6 +57,12 @@ impl LuaState {
         }
     }
 
+    pub fn pushbytes(&self, val: &[u8]) {
+        unsafe {
+            lua_pushlstring(self.lua, val.as_ptr() as *const c_char, val.len());
+        }
+    }
+
     pub fn pushinteger(&self, val: i64) {
         unsafe {
             lua_pushinteger(self.lua, val);