Fix JSON parsing in debugger code (#297)
Fix JSON parsing in debugger code (#297)

Some compilers generate header type descriptions that include
information about field signedness. The tools using the JSON need to
support both cases (with and without signedness information).
hanw/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,p4lang/behavioral-model