bgfx: expose ovrSession as platform data

vrdata.diff

diff --git a/include/bgfx/bgfxplatform.h b/include/bgfx/bgfxplatform.h
index f44bb82..497a109 100644
--- a/include/bgfx/bgfxplatform.h
+++ b/include/bgfx/bgfxplatform.h
@@ -82,6 +82,12 @@ namespace bgfx
 	///
 	const InternalData* getInternalData();
 
+	struct VRData
+	{
+		void* session; //!< ovrSession, when using LibOVR.
+	};
+	const VRData* getVRData();
+
 	/// Override internal texture with externally created texture. Previously
 	/// created internal texture will released.
 	///
diff --git a/src/bgfx.cpp b/src/bgfx.cpp
index e966e1c..9d80023 100644
--- a/src/bgfx.cpp
+++ b/src/bgfx.cpp
@@ -285,6 +285,7 @@ namespace bgfx
 	static bool s_renderFrameCalled = false;
 	InternalData g_internalData;
 	PlatformData g_platformData;
+	VRData       g_vrData;
 	bool g_platformDataChangedSinceReset = false;
 
 	void AllocatorStub::checkLeaks()
@@ -321,6 +322,11 @@ namespace bgfx
 		return &g_internalData;
 	}
 
+	const VRData* getVRData()
+	{
+		return &g_vrData;
+	}
+
 	uintptr_t overrideInternal(TextureHandle _handle, uintptr_t _ptr)
 	{
 		BGFX_CHECK_RENDER_THREAD();
diff --git a/src/bgfx_p.h b/src/bgfx_p.h
index 456d81e..3e82dd9 100644
--- a/src/bgfx_p.h
+++ b/src/bgfx_p.h
@@ -265,6 +265,7 @@ namespace bgfx
 {
 	extern InternalData g_internalData;
 	extern PlatformData g_platformData;
+	extern VRData       g_vrData;
 	extern bool g_platformDataChangedSinceReset;
 
 #if BGFX_CONFIG_MAX_DRAW_CALLS < (64<<10)
diff --git a/src/hmd_ovr.cpp b/src/hmd_ovr.cpp
index 960db03..c7df7b3 100644
--- a/src/hmd_ovr.cpp
+++ b/src/hmd_ovr.cpp
@@ -60,6 +60,8 @@ namespace bgfx
 			return;
 		}
 
+		g_vrData.session = (void*)m_session;
+
 		BX_STATIC_ASSERT(sizeof(_desc->m_adapterLuid) >= sizeof(luid));
 		memcpy(&_desc->m_adapterLuid, &luid, sizeof(luid));
 
@@ -121,6 +123,7 @@ namespace bgfx
 		if (NULL != m_session)
 		{
 			ovr_Destroy(m_session);
+			g_vrData.session = NULL;
 			m_session = NULL;
 		}
 	}