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>

ports/bdk-atxx4-mstp/bacnet.cproj

@@ -359,6 +359,10 @@
       <SubType>compile</SubType>
       <Link>BACnet Core\bacdcode.c</Link>
     </Compile>
+    <Compile Include="..\..\src\bacnet\bacdevobjpropref.c">
+      <SubType>compile</SubType>
+      <Link>BACnet Core\bacdevobjpropref.c</Link>
+    </Compile>
     <Compile Include="..\..\src\bacnet\bacerror.c">
       <SubType>compile</SubType>
       <Link>BACnet Core\bacerror.c</Link>
@@ -395,6 +399,10 @@
       <SubType>compile</SubType>
       <Link>BACnet Core\ihave.c</Link>
     </Compile>
+    <Compile Include="..\..\src\bacnet\hostnport.c">
+      <SubType>compile</SubType>
+      <Link>BACnet Core\hostnport.c</Link>
+    </Compile>
     <Compile Include="..\..\src\bacnet\lighting.c">
       <SubType>compile</SubType>
       <Link>BACnet Core\lighting.c</Link>