fixing HAVE_MAX_FRAGMENT ifdef
Boundaries check for server hello parsing.
-- added totalSz to the function parameters
-- INCOMPLETE DATA checked only once with hello size against buffer size
-- BUFFER_ERROR returned in case of message overflow (piece larger than the hello size)
-- OPAQUE16_LEN used whenever 2 bytes are needed.
-- Session id checking improved.
moving available data length check to DoHandShakeMsgType
removed duplicated check for INCOMPLETE_DATA
added new size enums
Boundaries check for DoClientKeyExchange.
-- switched from totalSz to size in the function parameters
-- BUFFER_ERROR returned in case of message overflow (piece larger than the hello size)
-- OPAQUE16_LEN used whenever 2 bytes are needed.