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/namespace_test/NamespaceC/TableInC.go

@@ -0,0 +1,46 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+package NamespaceC
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+type TableInC struct {
+	_tab flatbuffers.Table
+}
+
+func (rcv *TableInC) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *TableInC) ReferToA1(obj *TableInFirstNS) *TableInFirstNS {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		x := rcv._tab.Indirect(o + rcv._tab.Pos)
+		if obj == nil {
+			obj = new(TableInFirstNS)
+		}
+		obj.Init(rcv._tab.Bytes, x)
+		return obj
+	}
+	return nil
+}
+
+func (rcv *TableInC) ReferToA2(obj *SecondTableInA) *SecondTableInA {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		x := rcv._tab.Indirect(o + rcv._tab.Pos)
+		if obj == nil {
+			obj = new(SecondTableInA)
+		}
+		obj.Init(rcv._tab.Bytes, x)
+		return obj
+	}
+	return nil
+}
+
+func TableInCStart(builder *flatbuffers.Builder) { builder.StartObject(2) }
+func TableInCAddReferToA1(builder *flatbuffers.Builder, referToA1 flatbuffers.UOffsetT) { builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(referToA1), 0) }
+func TableInCAddReferToA2(builder *flatbuffers.Builder, referToA2 flatbuffers.UOffsetT) { builder.PrependUOffsetTSlot(1, flatbuffers.UOffsetT(referToA2), 0) }
+func TableInCEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT { return builder.EndObject() }