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/win32/Microsoft Visual Studio 2019/BACnet_Stack_Library/BACnet_Stack_Library.vcxproj

@@ -198,6 +198,7 @@
     <ClCompile Include="..\..\..\..\src\bacnet\indtext.c" />
     <ClCompile Include="..\..\..\..\src\bacnet\basic\sys\key.c" />
     <ClCompile Include="..\..\..\..\src\bacnet\basic\sys\keylist.c" />
+    <ClCompile Include="..\..\..\..\src\bacnet\hostnport.c" />
     <ClCompile Include="..\..\..\..\src\bacnet\lighting.c" />
     <ClCompile Include="..\..\..\..\src\bacnet\lso.c" />
     <ClCompile Include="..\..\..\..\src\bacnet\memcopy.c" />

ports/win32/Microsoft Visual Studio 2019/BACnet_Stack_Library/BACnet_Stack_Library.vcxproj.filters

@@ -90,6 +90,9 @@
     <ClCompile Include="..\..\..\..\src\bacnet\indtext.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\..\src\bacnet\hostnport.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\..\..\src\bacnet\lighting.c">
       <Filter>Source Files</Filter>
     </ClCompile>