Added checks for OPTIONAL context tagged decoding to be sure it is not a closing tag.
Added makefile for unit test in bacdevobjpropref.c module, and improved unit test.
https://sourceforge.net/p/bacnet/bugs/49/
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-context specific decoders for all of the primitive times to go with the context specific encoders
-unconfirmed/confirmed EventNotificationRequest structure/encoder/decoder
-BACnetTimestamp structure/encoder/decoder
-BACnetPropertyStates structure/encoder/decoder
-BACnetDeviceObjectPropertyReference structure/encoder/decoder
Changes:
-decode_context_object_id::object_type changed to uint16_t
-explicit casts have been added to some functions to remove compiler warnings
-encode_bacnet_date::year behaviour has been changed slightly