EAP-FAST: Cleaned up TLV processing and added support for EAP Sequences

EAP-FAST: Cleaned up TLV processing and added support for EAP Sequences

Number of TLVs were processed in groups and these cases were now separated
into more flexible processing of one TLV at the time. wpabuf_concat()
function was added to make it easier to concatenate TLVs. EAP Sequences are
now supported in both server and peer code, but the server side is not
enabled by default.