Codechange: be consistent in naming the paint function Paint()

Also move this function to be a class member. This to allow
further deduplicating of code in a later commit.

src/video/win32_v.h

@@ -47,6 +47,8 @@ protected:
 	void InputLoop() override;
 	bool LockVideoBuffer() override;
 	void UnlockVideoBuffer() override;
+	void Paint() override;
+	void PaintThread() override;
 
 private:
 	std::unique_lock<std::recursive_mutex> draw_lock;