Method erase

libcppcryptfs/context/cryptcontext.h:63–67

		m_handles.insert(h);
	}
	void erase(HANDLE h)
	{
		lock_guard<mutex> lck(m_mutex);
		m_handles.erase(h);
	}
	size_t size() {
		lock_guard<mutex> lck(m_mutex);
		return m_handles.size();