Add support for `with` construct

[fsestini]

This is to support definitions such as

(*** TLBI-after, DC-after, IC-after ***)
include "enumerations.cat"
with TLBI-after from (all-TLBI-Imp_TTD_R-enums local-hw-reqs)
with DC-after from (all-DC-Exp_W-enums local-hw-reqs)
with IC-after from (all-IC-Imp_Instr_R-enums local-hw-reqs)