Crypto support

Crypto support enables the encryption and decryption of the network frames.

It provides a framework for multiple encryption methods, such as WEP and null crypto. Crypto keys are mostly managed through the ioctl() interface and inside the ieee80211 layer, and the only time that drivers need to worry about them is in the send routine when they must test for an encapsulation requirement and call ieee80211_crypto_encap() if necessary.