BinaryIo: fix Reader::readValue().

std::fread() returns how many things it read, not the amount of
bytes read. Worst thing is, I got this right everywhere else.

src/BinaryIo/Reader.h

@@ -61,7 +61,7 @@ class Reader {
 
         template<typename T>
         bool readValue(T& value) {
-            return fread(&value, sizeof(T), 1, _file) == sizeof(T);
+            return fread(&value, sizeof(T), 1, _file) == 1;
         }
 
         template<std::size_t S>