Support binary search for struct in cpp (#4245)

* Support binary search for struct in cpp

CreateVectorOfSortedStruct is provided for convenience.

* fix continuous-integration error

* add generated files

* compile Ability.cs in csharp test

* compile Ability.cs in csharp

* modify according to code review

tests/MyGame/Example/Ability.php

@@ -0,0 +1,52 @@
+<?php
+// automatically generated by the FlatBuffers compiler, do not modify
+
+namespace MyGame\Example;
+
+use \Google\FlatBuffers\Struct;
+use \Google\FlatBuffers\Table;
+use \Google\FlatBuffers\ByteBuffer;
+use \Google\FlatBuffers\FlatBufferBuilder;
+
+class Ability extends Struct
+{
+    /**
+     * @param int $_i offset
+     * @param ByteBuffer $_bb
+     * @return Ability
+     **/
+    public function init($_i, ByteBuffer $_bb)
+    {
+        $this->bb_pos = $_i;
+        $this->bb = $_bb;
+        return $this;
+    }
+
+    /**
+     * @return uint
+     */
+    public function GetId()
+    {
+        return $this->bb->getUint($this->bb_pos + 0);
+    }
+
+    /**
+     * @return uint
+     */
+    public function GetDistance()
+    {
+        return $this->bb->getUint($this->bb_pos + 4);
+    }
+
+
+    /**
+     * @return int offset
+     */
+    public static function createAbility(FlatBufferBuilder $builder, $id, $distance)
+    {
+        $builder->prep(4, 8);
+        $builder->putUint($distance);
+        $builder->putUint($id);
+        return $builder->offset();
+    }
+}