ALLJOYN-2210 Fixed compiler warning from VC++

Changed the qcc::Crypto_AES::KeyState and the qcc::Crypto_Hash::Context from
classes to structs.

In the qcc/Crypto.h header file both are forward declared as structs.
(see Crypto.h lines 541 and 653) They are Opaque types for holding an internal
state.

This fixes the compiler warning C4099 - type name first seen using 'struct' now
seen using 'class'.

Change-Id: I476bafbbcd3de1493a7a01af5ad761c358c9c785