Feature/apdu null length returned (#285)

* Add APDU as NULL to get BACnet type lengths.

* Fix bacapp copy test to succeed

* fix BACnet REAL and DOUBLE decode

* Add unit test for NULL APDU encoding for length

* Add unit tests for bacapp context

* refactor host-n-port to hostnport.c module

* fix BVLC decoder

* additional unit testing for bacapp

* include bacdevobjpropref module in builds

* simplify bacapp snprintf to be able to return length

* adjust compiler for variable-length arrays

* fix bug found by scan-build

Authored-by: Steve Karg <skarg@users.sourceforge.net>

test/bacnet/basic/object/credential_data_input/CMakeLists.txt

@@ -48,6 +48,7 @@ add_executable(${PROJECT_NAME}
 	${SRC_DIR}/bacnet/datetime.c
 	${SRC_DIR}/bacnet/basic/sys/days.c
 	${SRC_DIR}/bacnet/indtext.c
+	${SRC_DIR}/bacnet/hostnport.c
 	${SRC_DIR}/bacnet/lighting.c
 	${SRC_DIR}/bacnet/timestamp.c
 	${SRC_DIR}/bacnet/wp.c