Missing macro error recovery

[pjaquiery]

Two issues:

if a macro is referenced in the Project Steps, but has not been defined, build fail processing happens but the FAILSTEP_NAME and FAILSTEP_OUTPUT macros are blank.

if a macro is referenced in the Failure Steps, but has not been defined, the build stops and the failure processing is not completed.

The big problem is in the failure step processing because often that is reporting the failure (generally by email for us). A fix would be for VBP to treat all undefined macros in failure step processing as defined but blank. That would generally allow the processing to complete at least.