Allow unions of table types with the same name but from different namespaces.

Also fixed most codegenerators using the wrong namespace when multiple
namespace were used in a file, with some files not being generated.

Change-Id: Ib42969221239d7244e431cbd667ef69200fc415f
Tested: on Linux.
Bug: 29338474

tests/MyGame/Example2/Monster.php

@@ -0,0 +1,79 @@
+<?php
+// automatically generated by the FlatBuffers compiler, do not modify
+
+namespace MyGame\Example2;
+
+use \Google\FlatBuffers\Struct;
+use \Google\FlatBuffers\Table;
+use \Google\FlatBuffers\ByteBuffer;
+use \Google\FlatBuffers\FlatBufferBuilder;
+
+class Monster extends Table
+{
+    /**
+     * @param ByteBuffer $bb
+     * @return Monster
+     */
+    public static function getRootAsMonster(ByteBuffer $bb)
+    {
+        $obj = new Monster();
+        return ($obj->init($bb->getInt($bb->getPosition()) + $bb->getPosition(), $bb));
+    }
+
+    public static function MonsterIdentifier()
+    {
+        return "MONS";
+    }
+
+    public static function MonsterBufferHasIdentifier(ByteBuffer $buf)
+    {
+        return self::__has_identifier($buf, self::MonsterIdentifier());
+    }
+
+    public static function MonsterExtension()
+    {
+        return "mon";
+    }
+
+    /**
+     * @param int $_i offset
+     * @param ByteBuffer $_bb
+     * @return Monster
+     **/
+    public function init($_i, ByteBuffer $_bb)
+    {
+        $this->bb_pos = $_i;
+        $this->bb = $_bb;
+        return $this;
+    }
+
+    /**
+     * @param FlatBufferBuilder $builder
+     * @return void
+     */
+    public static function startMonster(FlatBufferBuilder $builder)
+    {
+        $builder->StartObject(0);
+    }
+
+    /**
+     * @param FlatBufferBuilder $builder
+     * @return Monster
+     */
+    public static function createMonster(FlatBufferBuilder $builder, )
+    {
+        $builder->startObject(0);
+        $o = $builder->endObject();
+        return $o;
+    }
+
+    /**
+     * @param FlatBufferBuilder $builder
+     * @return int table offset
+     */
+    public static function endMonster(FlatBufferBuilder $builder)
+    {
+        $o = $builder->endObject();
+        return $o;
+    }
+}