Fix int vs. ssize_t type confusion

Plus a typo in the target type of a static_cast.

Change-Id: Icb8288baeab20d470c334742d989ffe231fdca7c
diff --git a/tools/ndnputchunks3.cpp b/tools/ndnputchunks3.cpp
index ca9475a..6eea0b7 100644
--- a/tools/ndnputchunks3.cpp
+++ b/tools/ndnputchunks3.cpp
@@ -40,7 +40,7 @@
     do
       {
         std::cin.read(buf, MAX_SEG_SIZE);
-        int got = std::cin.gcount();
+        ssize_t got = std::cin.gcount();
 
         if (got > 0)
           {