peek: add --hop-limit option

Change-Id: I1d0179f498ce70166085e6934e015ff4c00b4858
diff --git a/tools/peek/ndnpeek/ndnpeek.hpp b/tools/peek/ndnpeek/ndnpeek.hpp
index 357597e..998d049 100644
--- a/tools/peek/ndnpeek/ndnpeek.hpp
+++ b/tools/peek/ndnpeek/ndnpeek.hpp
@@ -49,6 +49,7 @@
   bool mustBeFresh = false;
   shared_ptr<Link> link;
   time::milliseconds interestLifetime = DEFAULT_INTEREST_LIFETIME;
+  optional<uint8_t> hopLimit;
   shared_ptr<Buffer> applicationParameters;
 
   // program behavior options