uses function starts as the entires when building the symtab

Uses the same initial starting points when building whole program CFG
and symbol table. This improves performance and prevents discrepancies
between the set of instructions discovered during the disassembly and
the set of instructions that are discovered when we build various
graph representations. In certain cases, e.g., in the interworked
binaries, such discrepancies could result in an abnormal termiantion
of a program.

lib/bap_disasm/bap_disasm_rec.ml

@@ -77,6 +77,7 @@ let has_conditional_jump blk =
 let global_cfg disasm =
   Driver.explore disasm
     ~init:Cfg.empty
+    ~entries:(Set.to_sequence@@Driver.subroutines disasm)
     ~block:(fun mem insns ->
         Driver.execution_order insns >>=
         KB.List.filter_map ~f:(fun label ->

lib/bap_disasm/bap_disasm_symtab.ml

@@ -174,6 +174,7 @@ let create_intra disasm calls =
 let create_inter disasm calls init =
   Disasm.explore disasm
     ~init
+    ~entries:(Set.to_sequence@@Disasm.subroutines disasm)
     ~block:(fun mem _ -> KB.return mem)
     ~node:(fun _ s -> KB.return s)
     ~edge:(fun src dst s ->